John & Richard: h from Az, dec, & Lat
Richard: You wrote: If you know the zenith distance, z, of the sun (90° - elevation angle) as well as the azimuth (A) then you could use: sin(h) = -sin(z)*sin(A)/cos(delta) where delta is the sun's declination. The latitude of the site, phi, is not needed. Computing the hour angle when the zenith distance is not known is a little trickier. In principle, this equation could be used: sin(h) = tan(A)*(sin(phi)*cos(h) - cos(phi)*tan(delta)) but you'll notice that h appears on both sides of the equation. Possibly this can be solved in an iterative fashion by selecting an approximate trial value for h and using it on the r.h.s. to compute a new value of h. You would then use this new value on the r.h.s. and continue the iterative procedure until the new value does not change significantly from the previous value. I've not actually tried this myself so proceed with caution. [endquote] Once, in an unfamiliar town, I wanted to find when the sun's direction is south, east, west, southeast, and southwest--for orientation in the new town. At first, I used the successive substitutions method that you describe above. As you suggest there, that method doesn't always work, but, when it does, it's convenient. But then I noticed that the equation can be solved as an equation quadratic in sin h. Just write cos h in terms of sin h, and put that term by itself on the left side of the equation. Square both sides. You get an equation quadratic in sin h. When dec is positive, then, to choose from the quadratic formula's 2 answers for sin h, it might be necessary to consider the requirement that the azimuth be north (or south) of the east-west line, as determined in the denominator of the azimuth formula. John: I'll soon post the resulting formula for h, given Lat, Az, and dec. Most likely someone else will post it before I do, though. I'm quite conscious of the fact that there are some people at is list, and in dialing, who are a lot more qualified than I am. Of course a frequent need to find h, given Lat, Az, and dec, is when it's necessary to find when a sundial won't be shaded by a building. Michael Ossipoff -- Richard Langley On Saturday, January 31, 2015, 31, at 11:05 AM, John Goodman wrote: >* Dear dialists, *> >* Does anyone know a formula for calculating the hour angle given the azimuth, declination, and latitude? *> >* I’d like to know the time of day, throughout the year, when the sun will be positioned at a particular angle. This will allow me to determine when sunshine will stream squarely through a window on any (sunny) day. *> >* I’ve seen several formulae for calculating azimuth. I suspect that one of them could be rewritten to solve for the hour angle given the azimuth instead of the finding the azimuth using the hour angle (plus the declination and latitude). Unfortunately, I don’t have the math skills for this conversion. *> >* Thanks for any suggestions. * --- https://lists.uni-koeln.de/mailman/listinfo/sundial
Jack: Duration of sunlight on a particular day
Jack: You wrote: *I have been trying to figure out how to plot the duration of daylight over *>* the course of the year as a function of latitude. (I would generate a *>* curve for each latitude I am interested in.)* *[endquote]* *You said to disregard physical effects such as atmospheric refraction (and solar semi-diameter?). That simplifies the formula.* *Where h is the number of equal sundial-hours before or after solar noon at sunrise or sunset; dec is declination, and Lat is latitude:* *cos h = - tan Lat * tan dec.* *Double h, and that's the sunlight duration for that day, the day corresponding to some particular value of dec, at some particular latitude Lat.* *And yes, _lots_ of people at this list know that. I'm not posting something new. But I just wanted to mention it because I haven't seen it in the answers so far.* *Michael Ossipoff* --- https://lists.uni-koeln.de/mailman/listinfo/sundial
John & Richard: h from Az, dec, & Lat
John:
(I don't know if each paragraph will be enclosed in asterisks. That
happened in one of my posts, but not in the other. I use an asterisk for
multiplaction and any spurious asterisk at the beginning and end of a
paragraph shouldn't be confuse with that multiplying asterisk.)
Here is the formula for h, for a given Az, Lat, and dec. ...which I said
that I'd soon post.
>From the size of this formula, it isn't surprising that others have
recommended something briefer. But this formula comes directly from the
formula for Az, from Lat, dec, & h.
This is in the form of a quadratic-formula solution. It can give 2 answers,
and I'll say something about how to choose which one is right.
What follows will be correct if I didn't make any algebraic errors.
I use these abbreviations:
Az = azimuth
Lat = latitude
dec = declination
h = hour angle (The sun's hour angle is the sundial equal-hours before or
after solar.noon).
(The Greek letters save space, when they're available, but not when they
have to be written out in Latin characters. And the above abbreviations are
clearer to people who aren't familiar with the Greek-letter symbols.)
h =
-2(tan dec * cos Lat)/tan Az plus-or-minus the square root of:
{4( tan^2 dec * cos^2 lat/tan^2 Az)
- 4(sin^2 Lat +1/tan^2 Az) * (tan^2 dec * cos^2 Lat -sin^2 Lat) }
The result of evaluating the above is divided by:
2 * (sin^2 Lat + 1/tan^2 Az)
-
Because the quadratic formula often gives 2 answers, then here are some
suggestions for choosing the right one:
If your input azimuth is east of south, then h and its sine must be
positive.
If your input azimuth is west of south, then h and its sine must be
negative.
If your input azimuth is south of the east-west line, then the cosine of h
must be greater than:
tan dec/tan Lat.
.if your input azimuth is north of the east-west lilne, the cosine of h
must be less than tan dec/tan Lat.
Maybe a briefer solution-fomula can be gotten by setting equal to zero, the
sun's altitude in a co-ordinate system whose "equator" is the azimuth
circle passing through your desired azimuth, and solving for the h that
would achieve that.
If that's workable, then it could have the advantage that h only appears
once in the altitude formula.
I apologize in advance for any algebraic or copying errors.
Michael Ossipoff
---
https://lists.uni-koeln.de/mailman/listinfo/sundial
John & Richard: h from Az, dec, & Lat
Sorry, I accidentally wrote " h = ", when I meant " sin h = ", at the beginning of the formula for h, given Az, Lat, and dec. Michael Ossipoff --- https://lists.uni-koeln.de/mailman/listinfo/sundial
John & Richard: h from Az, dec, & Lat
I'm sorry--another typo: I meant to say: If your input azimuth is west of south, then h and its sine must be positive. If your input azimuth is east of south, then h and its sine must be negative I really didn't mean to post so much, but I wanted to correct those typos. Michael Ossipoff --- https://lists.uni-koeln.de/mailman/listinfo/sundial
John & Richard: h from Az, dec, & Lat
Another omission: By "Az", I ;mean your desired azimuth, expressed in angular distance-in-azimuth from north or south, whichever of those distances is less (depends on whether your intended azimuth is closer to north or to south).. The appeal of the briefer solution that someone else posted is clear. Ok, I don't think there will need to be any more fixes or corrections by me. Again, sorry about the omissions and typos, and the necessary corrections and fixes. Michael Ossipoff --- https://lists.uni-koeln.de/mailman/listinfo/sundial
Neater, briefer, presentaton of h solution, given Az, Lat, & dec
John & Richard: Whatr a sloppy mess my posting was, where I told the solution for h. This is a better way to present it, and a neat, convenient way to evaluate the solution: The quadratic formula: [-b +/- sqrt (b^2 - 4ac] / 2a -- a,b, & c, for this solution: a = sin^2 Lat + 1/tan^2 Az b = 2 tan dec cos Lat / tan Az c = tan^2dec cos^2 Lat - sin^2 Lat - By the quadratic formula: sin h = [-b +/- sqrt(b^2 - 4ac] / 2a Constraints on h: If intended azimuth is west of the north-south line, then h and its sine are positive If intended aziuth is east of the north-south line, then h and its sine are negative. If intended azimuth is south of the east-west line, then cos h > tan dec / tan Lat. If intended azimuth is north of the east-west line, then cos h < tan dec / tan Lat. ------ Michael Ossipoff If intened azimuth is north of the east-west line, then cos h < tan dec --- https://lists.uni-koeln.de/mailman/listinfo/sundial
h from Az. Question about iterative solution of equations.
I realize that methods for solving equations that don't have an exact solution ( a solution in closed form) might be a little off-topic here. But, indirectly, it's a sundial question, because most likely there are sundial problems that result in equations without an exact solution. For example, in the earlier discussion about finding azimuth, when h, dec, and Lat are known, there was some discussion of an iterative solution by Successive Substutions. I pointed out that the equation has an exact solution. But that discussion brought out the relevance of iterative equation solutions to the sundial topic. My question is about one particular relatively new version of Regula Falsi, described by some university mathematicians, in a paper. The page with the paper doesn't show a url, but here is the url of the google page a which their paper can be found and linked to.It's the link that says "An Improved Regula Falsi Method..." : https://www.google.com/#q=Naghipoor%2C+J.%2C+Ahmadian+S.A.%2C+and+Soheili%2C+A.R.%2C+%E2%80%9CAn+ImprovedRegula Newton's Method is deservedly popular, because it rarely fails to converge, and its convergence is usually very fast, especially if the initial guess is close. Of course it doesn't always converge, and sometimes only converges slowly. At the oppose extreme is Bisection, which _reliably_ converges at a predictable, respectable and useful (but not spectacular) rate. Regula Falsi is appealing, because it, too, always converges. And it has many improved versions that offer to make converge faster than Bisection except with the most deviously pathological equations. Maybe the sheer number of Regula Falsi improvements proposed is an indication of that methods promising-ness. Anyway, the paper referred to above is about one of those improved Regula Falsi methods. That's the subject of my question: The paper tells the proposed procecure, but it says nothing about the justification or motivation for the procedure. So, my question is, if anyone is interested in Regula Falsi improvements, can anyone tell me what is the justification or motivation for the procedure described in the paper that I mentioned above? (I emphasize that it isn't the only improved linear Regula Falsi version) Evidently the Regula Falsi versions usually requiring the fewest function-evaluations are the ones that replace Regula Falsi's linear interpolation with a curve--quadratic, inverse-quadratic, or exponential. But they require more work for each iteration. The paper that I referred to only compares its method to ordinary, un-improved Regula-Falsi, a method that probably isn't advocated anymore. But the authors seem to imply that their method compares well to other linear Regula Falsi methods. Michael Ossipoff --- https://lists.uni-koeln.de/mailman/listinfo/sundial
Mayall & Mayall's Reclining-Declining formulas
If anyone has a copy of Mayall & Mayall's sundial book, could that someone post, here (or send to me by individual e-mail, if preferred) Mayall & Mayall's Reclining-Declining formulas (of course with the definitions for what the symbols stand for)? Additionally, and this is probably asking a bit too much, but could someone also post Rohr's Reclining-Declining formulas if someone has them? Of course a link to those formulas, or instructions for finding them on the web, would be fine too. On another, related, topic, would anyone like to work (no amount of work is too small) on the Wikipedia article on sundial's? ...if anyone has time to do a fix or two, a correction or addition, etc. Modifying the article doesn't require membership, registration, or signing-in. Of course any positive modification, however brief or small, would be beneficial. In particular, can anyone suggest or make changes or improvements to that Wikipedia article's "Reclining-Declining" section, or comment on it at that article's "Talk" page? Michael Ossipoff --- https://lists.uni-koeln.de/mailman/listinfo/sundial
Wikipedia says Mayall & Mayall's, and Rorh's formulas are wrong.
Sorry, I didn't intend to start new thread; I'm adding something to my Mayall & Mayall question-post: First, I thank Simon for the answer and link. I've decided to divulge the reason for my question about Mayall & Mayall: The wikipedia Sundial article says that Mayall & Mayall, and Rohr as well, published incorrect Reclining-Declining formulas. In fact, the wikipedia sundial article also says that only in the last decade has there been agreement on the formula for a Reclining-Declining sundial. Those claims aren't supported in the article. Are they correct? I invite dialists to check out those claims, and modify or delete them in the wikipedia article. As I said, the article can be edited, modified, or deleted by anyone, without membership, registration or log-in. And, in general, the wikipedia sundial article needs some input from dialists. Come on, let's (at least in part) start fixing that wikipedia article, which is surely many people's introduction to sundials. I like sundials, and I don't like to be contentious about a subject that I like. And the Internet already has too much contentiousnes. But should unsupported or incorrect statements that contradict everything previously published be at that introductory article? Michael Ossipoff --- https://lists.uni-koeln.de/mailman/listinfo/sundial
Mayall & Mayall formulas are correct for a horizontal dial.
The Mayall & Mayall Reclining-Declining formulas given in the notes for the wikipedia sundial article give the right answer for a horizontal dial. ...if R is taken as the inclination from the horizontal, and (as the author of that wikipedia article section defined it) D is the azimuth that the up-tipped dial is facing. Then, if R = 0, and D = 0 (a horizontal dial), the Mayall & Mayall Reclining-Declining formulas in the notes give the right answers. I like the word "inclining" better than "reclining", because "reclining" implies distance from the vertical. But departure from the horizontal is how the dial departs from a horizontal dial, the ordinary dial. For example, as I mentioned, a horizontal has R = 0 and D = 0, when R is defined as departure from the horizontal. As I mentioned before, differences in how variables are defined can result in different but equivalent formulas. ...which might mistakenly be judged as incorrect for that reason. Michael Ossipoff --- https://lists.uni-koeln.de/mailman/listinfo/sundial
Wikipedia says Mayall & Mayall's, and Rorh's formulas are wrong.
Additionally, Mayall & Mayall's formula (shown in the notes at the bottom of the wikipedia Sundial article) for the angle between the substyle and the line for noon, gives the right result for: Lat = 51.5 Inclination = 45 Declination = 45 degrees left of south Michael Ossipoff --- https://lists.uni-koeln.de/mailman/listinfo/sundial
Wikipedia says Mayall & Mayall's, and Rorh's formulas are wrong.
I should add that the correct result described above, with Mayall & Mayall's formula for the angle between the substyle and the line for noon, is gotten when the decline-direction (D) is measured from north. So D is the azimuth that the dial is facing. Michael Ossipoff --- https://lists.uni-koeln.de/mailman/listinfo/sundial
The other Mayall & Mayall formula (in the wikipedi article notes) likewise gives the correct answer.
The other of the 2 Reclining-Declining formulas listed in the notes, at the bottom of the wikipedia Sundial article, likewise gives correct answers. Again, using: Lat = 51.5 Incline = 45 Decline direction = 45 degrees left of south ...The Mayall & Mayall formula, in the article's notes, for Hrd--gives the correct answer for the angle between the 8:00 a.m. line and the noon line on the dial. If the line for a particular hour is counterclockwise from the noon line, then that answer is given as negative, (or maybe under some circumstances, as the positive number consisting ofthe sum of that negative + 360). Let me repeat some things about the use of those formulas: Where Hrd1 and Hrd2 appear at the left side of the two equations, Hrd1 should be replaced by tan Hrd1, and Hrd2 should be replaced by tan Hrd2. The equation Hrd = Hrd1 + Hrd2 is correct as shown. D, the decline direction, is measured from north. It's the azimuth that the dial is facing. R, the recline, is measured from the horizontal. (Nowadays that's probably more often called "incline" and represented by "I"). So, both of the Mayall & Mayall Reclining-Declining formulas in the notes at the bottom of the wikipedia Sundial article are correct, and give the correct answer. MichaelOssipoff --- https://lists.uni-koeln.de/mailman/listinfo/sundial
Wikipedia says Mayall & Mayall's, and Rorh's formulas are wrong.
Here is what wikipedia says, regarding formulas for Reclining-Declining sundials: "In fact it is only in the last decade that agreement has been found on the correct hour angle formula for this type of dial. [...] Previous formulae given by Rohr and Mayall are not correct." That wikipedia statement is demonstrably, preposterously, ridiculously incorrect. I deleted it, and one of the wikipedists immediately re-posted it. As I mentioned before, the wikipedia article, in its notes at the bottom of the page, in note (b), shows some formulas from Mayall & Mayall--the ones that wikipedia says are incorrect. And, as I mentioned, I tried those formulas, and they gave the correct answer--right down to the calculator's last digit--for the hour-line position for the two times of day that I I input (8:00 a.m. and noon), for a Reclining-Declining dial. Wikipedia has a firm policy against having any statements without citation, but the abovequoted statement is in the wikipedia Sundial article without any citation. Evidently the wikipedist who re-posted that statemet wants the wikipedia Sundial article to remain a laughingstock. Michael Ossipoff ~ 26 N, 80W --- https://lists.uni-koeln.de/mailman/listinfo/sundial
Does anyone have, or have access to, Compendium vol.12, #1, March 2005?
Alright, I realize that tryng to fix Wikipedia is like trying to bail-out the ocean with a thimble. But there's one little matter that I don't intend to let pass: Wikipedia's Sundial article says (regarding Reclining-Declining dials): "In fact it is only in the last decade that agreement has been found on the correct hour angle formula for this type of dial [...] Previous formulae given by Rohr and Mayall are not correct." As I mentioned in a previouis post, the Mayall & Mayall formulas that Wikipedia quotes, miscopied, in a note to the article, give the correct answers, for arbitrarily chosen latitude, recline, decline-angle and time-of-day--right down to the last decimal place on the calculator. ..when a few copying errors and variable-misinterpretations are fixed. Anyway, Wikipedia's big emphasis is on citation of notable sources, especially for any implausible or surprising statements (like those quoted above). The ony citation that's positioned anywhere near the abovequoted passage is to Compendium, vol. 12, #1, March 2005. ...in an article entitled "Sundial Design Using Matrices". The person who re-posted that passage after I deleted it won't answer my question about whether or not that article is the source of that statement (It could just have been intended as a reference for that sentence's mention of the use of matrices). I'd like to get to the bottom of the matter of where Wikipedia got the abovequoted statements. So, could someone take a look at that Compendium article, and tell me if it says anything that supports the abovequoted statements--and, if so,what it says? I'd appreciate it if you'd paste its words on that matter into a post here, or an e-mail to me ( at email9648...@gmail.com). thank you Michael Ossipoff ~ 26N, 80W --- https://lists.uni-koeln.de/mailman/listinfo/sundial
Horizontally-Viewed, All-Day, All-Year, All-Viewing-Directions Dials
dial. Michael Ossipoff --- https://lists.uni-koeln.de/mailman/listinfo/sundial
Aurora, the beginning of the arrival of Dawn
Some years ago, I was invited to go to the beach the following morning, to observe the sunrise. . I preferred getting there well before sunrise, but I didn’t know how early she was willing to start, and so I suggested that we meet at a time that would get us there a little before Civil Twilight. . She said, “That late?” . Good, we agreed then. So I suggested something better: A meeting time that would get us to the beach a little before Nautical Twilight. She said that sounded better, and we agreed on that meeting-time. I’d written-down the time at which Civil Twilight would start. But, somewhat before that time, it was clear that Dawn, Civil Twilight, was *beginning* to arrive. The beginning of the arrival of Civil Twilight was definitely clearly there. That interested me. . Though the arrival of full Civil Twilight is practical for a number of reasons, the *beginning *of its arrival seemed more significant, more beautiful, to me. . So I wrote the time down, at that time. . It was a time when the altitude of the sun was about -9.37 degrees. . (Though I rounded to the nearest hundredth of a degree, I can’t guarantee that all the inputs were accurate enough to justify that precision.) . As I said, that beginning, having a special beauty, seemed more significant to me than the arrival of full Civil Twilight. . Later, I read that evidently that time in the morning was recognized in Roman and Medieval times, and was given a name. . In those days, when people were living closer to nature, getting up earlier, and without pervasive night-time artificial light, they recognized several significant times in the morning: . Sunrise: Self explanatory Dawn: . This was a distinct time, before Sunrise. Surely it referred to the beginning of Civil Twilight, the time when it’s first fully light enough to look and feel like daytime. …when it’s first light enough to read or do daytime activities, or to go safely. . Aurora: . This was the beginning of the arrival of Dawn. …named after the Roman goddess of Dawn. . That’s what I’d noticed, and recorded the time of, at the beach! . So: Unless someone else suggests a different time, I suggest that Aurora is the time when the Sun’s altitude is -9.37 degrees. . Check it out, next time you’re up early. . By the way, if you aren’t up at least a little before Nautical Twilight, then you aren’t really up early. . p.s. . On another topic: I wasn’t going to bother you about this in a separate posting, but, since I’m posting anyway, I might as well include it: . In my previous post, I was talking about sundials that have the best overall readability, in terms of time-of-year, time-of-day, and viewing-direction. . After posting that, it occurred to me that I’d left something out: A 2-sided translucent equatorial dial with an equatorial disk, and also an equatorial band. …all translucent. . The equatorial band could be affixed to the equatorial disk, via tabs. …like the Band-Equatorial dial described in Teacher’s Corner, at the NASS website. . That article made the useful suggestion of constructing a Band-Equatorial by affixing a flexible band to a circular edge--in that instance, the edge of a circular cut in a piece of cardboard—via tabs. . But that circular edge could also be the edge of a circular disk. For a table dial, viewed from above, the circular cut is best. . But, for a high-mounted dial, viewed from below, a disk is best. And so it might as well be a translucent equatorial band affixed (by tabs) to a 2-sided translucent Equatorial Dial. …actually, one such band affixed to each side of that disk. . Such a dial would be readable edge-on (in the plane of the disk). . If the band is narrow, then it won’t significantly interfere with the viewing of the disk, or the opposite side of the band (for someone to whom their side of the band isn’t readable because it’s morning and s/he’s east of the dial, nearly in the plane of the disk). . Surely such a dial would have the best overall readability in terms of time-of-year, time-of-day, and viewing-direction. ...with the Equatorial's added advantage of simplicity of explanation. . …but would take longer to build than a plain 2-sided translucent Equatorial, or Vertical Declining, or Reclining-Declining dial. . Michael Ossipoff --- https://lists.uni-koeln.de/mailman/listinfo/sundial
Fwd: Aurora, the beginning of the arrival of Dawn
Anne-- Thanks for your reply. On Thu, Jun 11, 2015 at 4:26 AM, Bruvold Anne < anne.bruv...@nordnorsk.vitensenter.no> wrote: > Just a comment from the far north on Dawn and Aurora: > Aurora is the name of the light at dawn. > Yes, an edition of the Houghton Mifflin Dictionary gives these definitions of "Aurora": 1. The Roman goddess of the dawn 2. The dawn 3. a) Aurora Borealis b) Aurora Australis ...except that, in Roman and medieval times, "Aurora" didn't refer to the dawn (the full arrival of Civil Twilight) itself, but to the _beginning_ of the arrival of dawn. That's an important distinction. My definition, above, is one that I've only found in one source: A library book about time-reckoning throughout history. But its author evidently researched, in detail, the several Roman/medieval words for significant times during the morning. Though I only know of that one source that supports my definition, it's the only source I've encountered that treats the subject in detail at all. An edition of Merriam-Webster gives the same definitions, except, in different order: 1. Dawn 2. The Roman goddess of dawn 3. Aurora Borealis or Australis. > The full name of green flaming bands visible at night in the far north and > south is Aurora Borealis and Aurora Australis. The name Aurora Borealis was > given because the light as sees from middle Europe it resembles dawn, but > was not dawn. Hence it got the addition Borealis. As the same phenomenon > later was observed in the far south, the southern version got the addition > Australis. > Yes. > > Today the single word "Aurora" is no longer commonly used for the light at > dawn, and is more often associated with the light phenomenon in the upper > atmosphere. > Yes, I concede that nowadays "Aurora" is never, or nearly never, used with its original meaning--the beginning of the arrival of dawn. ...and that it's always, or nearly always, used to refer to the upper-atmosphere phenomenon of the far north and the far south. I've never seen the Aurora Borealis, and I know that I've thereby been missing something impressive. Though I use the word "Aurora" with its original ancient meaning that's practically unknown nowadays, it's the only word I know of, for that time of morning--the beginning of the arrival of dawn. I just don't know of any other word for it. It's something that people were more familiar with long ago, when rising earlier, living closer to nature's time, without any streetlights. I envy people who live in Australia or Norway, and I don't mind admitting that I'd quickly trade places. Here in Florida, though not technically the tropics, it's tropical in a number of ways: At summer-solstice noon, the sun is so nearly straight up that a person can't really tell that it isn't. You can't find your shadow unless you look straight down. In the summer, we're in the Trade Winds, the tropical easterlies. I must say that I like the intense sunshine and the warm "winter" temperature here, but the ultraviolet poses a skin-cancer risk. My ancestors came from Northern Europe (Britain and Russia), and so I'm not really designed for this latitude. All sorts of insects and lizards everywhere. I've seen 5 alligators during my 9 years in Florida. Climate-wise, I like Florida, but I'd trade places because I've heard only good things about Australia and Scandinavia. Michael Ossipoff 26N, 80W > > - Reply message - > Fra: "John Pickard" > Til: "sundial@uni-koeln.de" > Emne: Aurora, the beginning of the arrival of Dawn > Dato: tor., juni 11, 2015 01:30 > > > > > Hi Michael, > > You are making life far too complicated by worrying about which definition > of sunrise to use for your assignation. > > Here in Australia, if you are invited by a young (or older) woman to view > a sunrise from a beach, the only questions to be asked are “how much food > and beer / wine do I bring?” and “are you bringing the picnic rug?” > > But we are now in grip of winter in Sydney, and only the truly brave (or > those well fortified by alcohol anti-freeze) would venture to the beach in > the vain hope of glimpsing the dawn through the clouds. > > I’m not too sure about using “aurora” in the context of dawn. I spent many > hours lying in the snow in winter (~ –30C) in Antarctica looking up at > auroras, and it’s something I’ve never forgotten. Whether rippling sheets > of light, or shooting beams, they were pure magic. Far, far better than any > sunrise. > > Cheers, John > > John Pickard > john.pick...@bigpond.com > > > --- > https://lists.uni-koeln.de/mailman/listinfo/sundial > > > --- https://lists.uni-koeln.de/mailman/listinfo/sundial
Fwd: Aurora, the beginning of the arrival of Dawn
Hi John-- As I was saying in my reply to Anne, I'd trade places with residents of Australia or Europe, in a New York minute. Yes, by the way, I agree with the Australian designation for when summer and winter begin: Here, it's obvious that summer arrives with June, especially in the parts of the country which have distinct seasons. So I agree with the designation in Australia that says that summer arrives with December, and winter arrives with June. Here, for some reason, our astronomers have decided to define "summer" as beginning at the summer solstice, and to define "winter" as beginning at the winter solstice. There's not really any justification for those arbitrary designations. Once I telephoned an astronomer who always announces the beginning of the seasons, defined in his silly way, on the radio. I explained to him that he should just speak of "astronomical quarters", because his "seasons" have nothing to do with the actual seasons, as we all perceive them. He finally defended himself by saying that he didn't invent those astronomical "season"-designations. But he was still proclaiming them on the radio when the next solstice or equinox arrived. Everyone here (except the astronomers and the broadcasters who quote them) knows that, by the time June 21 arrives, it has already been summer for a long time. Michael Ossipoff 26N, 80W On Wed, Jun 10, 2015 at 7:30 PM, John Pickard wrote: > > Hi Michael, > > You are making life far too complicated by worrying about which definition > of sunrise to use for your assignation. > > Here in Australia, if you are invited by a young (or older) woman to view > a sunrise from a beach, the only questions to be asked are “how much food > and beer / wine do I bring?” and “are you bringing the picnic rug?” > > But we are now in grip of winter in Sydney, and only the truly brave (or > those well fortified by alcohol anti-freeze) would venture to the beach in > the vain hope of glimpsing the dawn through the clouds. > > I’m not too sure about using “aurora” in the context of dawn. I spent many > hours lying in the snow in winter (~ –30C) in Antarctica looking up at > auroras, and it’s something I’ve never forgotten. Whether rippling sheets > of light, or shooting beams, they were pure magic. Far, far better than any > sunrise. > > Cheers, John > > John Pickard > john.pick...@bigpond.com > > > --- > https://lists.uni-koeln.de/mailman/listinfo/sundial > > > --- https://lists.uni-koeln.de/mailman/listinfo/sundial
Re: Fwd: Aurora, the beginning of the arrival of Dawn
Richard-- Thanks; that's in agreement with how we all perceive summer and winter. I'd say that the astronomers and the newscasters and radio-personalities should listen to the meteorologists. Thanks again Michael Ossipoff 26N, 80W On Thu, Jun 11, 2015 at 11:39 AM, Richard Mallett < postmas...@rmallett.plus.com> wrote: > On 11/06/2015 16:21, Michael Ossipoff wrote: > >> >> >> Hi John-- >> >> As I was saying in my reply to Anne, I'd trade places with residents of >> Australia or Europe, in a New York minute. >> >> Yes, by the way, I agree with the Australian designation for when summer >> and winter begin: >> >> Here, it's obvious that summer arrives with June, especially in the parts >> of the country which have distinct seasons. >> >> So I agree with the designation in Australia that says that summer >> arrives with December, and winter arrives with June. >> >> Here, for some reason, our astronomers have decided to define "summer" as >> beginning at the summer solstice, and to define "winter" as beginning at >> the winter solstice. There's not really any justification for those >> arbitrary designations. Once I telephoned an astronomer who always >> announces the beginning of the seasons, defined in his silly way, on the >> radio. I explained to him that he should just speak of "astronomical >> quarters", because his "seasons" have nothing to do with the actual >> seasons, as we all perceive them. He finally defended himself by saying >> that he didn't invent those astronomical "season"-designations. But he was >> still proclaiming them on the radio when the next solstice or equinox >> arrived. >> >> Everyone here (except the astronomers and the broadcasters who quote >> them) knows that, by the time June 21 arrives, it has already been summer >> for a long time. >> >> Michael Ossipoff >> 26N, 80W >> > > For meteorologists, winter is DJF, Spring is MAM, Summers is JJA, Autumn > is SON. > > > -- > -- > Richard Mallett > Eaton Bray, Dunstable > South Beds. UK > > --- https://lists.uni-koeln.de/mailman/listinfo/sundial
Can I share Universal Analemmatic Sundial image?
I know that often one shouldn’t share an organization’s printed materials. Is it alright to send, to individuals, a copy of one of NASS’s PowerPoint files with the image of the Universal Analemmatic sun compass? Taking the question a step farther, it it alright to post it at a forum discussion of methods for solar direction-finding? That’s an ingenious device, and I was surprised to find out that it was first introduced no later than 1660. The “N” at the noon direction puzzled me at first, until I realized that it was the direction of a shadow at noon, not the sun. That sun-compass is a particularly useful, convenient and versatile one, because it can be used even when it isn’t in the sunlight. If you’re in a car or train, and shadows of telephone poles are visible outside your window, then the device can give north, by showing the angle between north and a shadow’s direction. Thanks to NASS and to Fred Sawyer for those images of the Universal Analemmatic sun-compass. Michael Ossipoff 26N, 80W --- https://lists.uni-koeln.de/mailman/listinfo/sundial
Re: Can I share Universal Analemmatic Sundial image?
Roger and Patrick: (addressed separately below) Roger-- Thanks for the answer. I wanted to find out what NASS permits. It permits, in the case of the Universal Analemmatic sun-compass image, sending 1 copy to any of 1 or more individuals, but it doesn't permit posting an image to forums. That's what I wanted to find out. In a week or a few weeks, I'll ask, here, if it's permissible to post, to a forum, a link to a NASS webpage that has an image of the Universal Analemmatic sun-compass...and, if so, what URL to link to. I won't ask that question today, because I've already asked a question and gotten an answer today. Michael Ossipoff Patrick-- Thanks for the reply. You wrote: Far better to contact the author, (or here NASS) to get permission for what you want to do [endquote] Yes, and that's what my posting was doing Though I didn't write directly to official NASS e-mail addresses, I knew that NASS's representatives could be reached at this forum. Michael Ossipoff --- https://lists.uni-koeln.de/mailman/listinfo/sundial
Another movie with a sundial
Another movie with a sundial: A 1965 English-subtitled foreign movie called *Terror Creatures from the* *Grave* had a character describing and showing a sundial. It was an azimuth dial, admittedly not an old or fancy one. It didn’t read in hours. It just marked one solar azimuth. In fact, it consisted of two sticks, vertically sticking in the ground. A long stick and a short one. Two characters were walking along the shore, and the woman called the man’s attention to something on the ground. He said, “What is it?”. She said it was a sundial that her father used to use to find out when the fish were biting. When the long stick’s shadow pointed toward the short stick, he would take his boat into the reeds. Of course one would expect fish to respond more to solar *altitude* than to azimuth. But there could have been a tree, or a vertical cliff-edge or building, that began or ceased to shade the fishing-spot at a certain solar azimuth. Michael Ossipoff --- https://lists.uni-koeln.de/mailman/listinfo/sundial
Re: Tarzan's sundial
Sasch: The International Movie Data-Base (IMDb) lists 10 Tarzan movies for the '50s. But Johnny Weismuller isn't in any of them. It's Lex Baxter (or Barker?) until Gordon Baxter took over in 1955. Here's the list: 1950: Tarzan & the Slave Girl (Lex Baxter) 1951: Tarzan's Peril (Lex Baxter) 1952: Tarzan's Savage Fury (Lex Baxter) 1953: Tarzan & the She-Devil (Lex Baxter) 1955: Tarzan's Hidden Jungle (Gordon Scott) 1957: Tarzan & the Lost Safari (Gordon Scott) 1958: Tarzan & the Trappers (Gordon Scott) 1958: Tarzan's Fight for Life (Gordon Scott) 1959: Tarzan's Greatest Adventure (Gordon Scott) 1959: Tarzan the Ape Man (Gordon Scott) Look at the synopses of those movies. Maybe one of them will have something familiar from the movie of interest. When you find the right one, or some possibilities for the right one, check to find out if it's on YouTube. Michael Ossipoff On Sat, Jul 18, 2015 at 12:16 AM, sasch stephens wrote: > There is a Tarzan movie, maybe with Johnnie Weissmiller from the 1950's > which might have been > the inspiration for the Terror Creatures film. I've been hoping to find > the clip for 30 years to be used as part of a sundial exhibition. It's too > good! > > The scene in question finds Tarzan in the jungle with two obviously > sinister characters near their twin prop plane. Tarzan is telling them > that they are not welcome there and takes two sticks, one small and one > large and vigorously sticks them in the ground and says, "When the shadow > of the tall stick passes the small stick, you must be gone". It fits in so > well with the primal forces of the jungle. > > I've been in search of this clip for years, anyone know how to find it? > Sasch Stephens > > > > -- > Date: Fri, 17 Jul 2015 08:47:05 -0400 > Subject: Another movie with a sundial > From: email9648...@gmail.com > To: sundial@uni-koeln.de > > Another movie with a sundial: > > > A 1965 English-subtitled foreign movie called *Terror Creatures from the* > *Grave* had a character describing and showing a sundial. > > > It was an azimuth dial, admittedly not an old or fancy one. It didn’t read > in hours. It just marked one solar azimuth. > > > In fact, it consisted of two sticks, vertically sticking in the ground. A > long stick and a short one. > > > Two characters were walking along the shore, and the woman called the > man’s attention to something on the ground. He said, “What is it?”. She > said it was a sundial that her father used to use to find out when the fish > were biting. When the long stick’s shadow pointed toward the short stick, > he would take his boat into the reeds. > > > Of course one would expect fish to respond more to solar *altitude* than > to azimuth. > > > But there could have been a tree, or a vertical cliff-edge or building, > that began or ceased to shade the fishing-spot at a certain solar azimuth. > > > Michael Ossipoff > > --- > https://lists.uni-koeln.de/mailman/listinfo/sundial > --- https://lists.uni-koeln.de/mailman/listinfo/sundial
Re: Tarzan's sundial
Barry-- Thanks for finding that scene! -- Barry, Sasch & all-- Of course Tarzan’s sundial was more for measuring *duration*, rather than time-of-day. “Get out of the jungle before this duration is up!” I once used a stick Azimuth Sundial for that same purpose, to measure a duration for someone who didn’t have a watch: My girlfriend at that time and I had been at the beach for some time, and she was about to go to visit with a group of women who met daily at Carls’ Junior fastfood restaurant. There was some item at her house (I don’t remember what it was) that she wanted to have with her when she left the beach. I offered to walk to her place to find it, and bring it to her at the beach. But, in case I couldn’t find it, I told her to go ahead and leave for the restaurant after a certain duration. She didn’t have a watch, and so I made a vertical-stick Azimuth Dial, on a horizontally-smoothed area of sand, using a thin straight stick as the gnomon. I marked a small point in the sand, and told her that, if I haven’t returned by the time the stick’s shadow reaches the mark, then to go ahead and go to the restaurant meeting, because I couldn’t find the item. I estimated how long it would take me to make the round-trip to her house, and to find the item. How I determined where to make the mark: I determined it based on a solar direction-finding method that I’ve used for a long time. I call it the “Altitude Watch Method” (AW), because it’s an improvement on the familiar “Watch Method” (W), described in so many books and articles. AW is an approximation to the navigators’ “Time-Altitude Method” (TA). TA says: sin Az = sin h * (cos dec/cos Alt). AW’s approximation consists of assuming that Az and h are proportionally-related in the same way as sin Az and sin h. At least some of the times when an Altitude Dial based on AW gives its best estimates of the rate-of-change of Az are when the duration is short enough so that the sun’s altitude doesn’t change a lot, and: …1) h is small Or …2) the sun’s altitude and the magnitude of its declination are small. But I tested the method, and found it to give good accuracy on the occasions when I tested it. Maybe those occasions weren’t too far from solar high noon, and that would explain the accurate results. But, as an approximate measure of duration, where exact time-of-day isn’t needed, the method should be satisfactory anytime. Though I tested it a few times, I only actually *used* it on that one occasion at the beach. Michael Ossipoff 26N, 80W On Sun, Jul 19, 2015 at 12:32 PM, Barry Wainwright wrote: > The film is the 1942 “Tarzan’s New York Adventure” and the scene is about > 6 minutes in. > > I’ve uploaded a clip of the scene to You Tube, you can find it at > https://youtu.be/G-Of5dyGq38 > > -- > Barry > > > > > On 18 Jul 2015, at 23:29, sasch stephens wrote: > > > > Thanks Michael, you've inspired me to start reviewing Tarzan movies, I > see that it is a daunting task, there are a lot of them and go back into > the 1930s. It will be a stroke of luck to find the right one. > > But for a sundial guy, it's such a special clip.Sasch > > > > Date: Sat, 18 Jul 2015 12:28:42 -0400 > > Subject: Re: Tarzan's sundial > > From: email9648...@gmail.com > > To: sasch...@hotmail.com > > CC: sundial@uni-koeln.de > > > > Sasch: > > > > The International Movie Data-Base (IMDb) lists 10 Tarzan movies for the > '50s. > > > > But Johnny Weismuller isn't in any of them. It's Lex Baxter (or Barker?) > until Gordon Baxter took over in 1955. > > > > Here's the list: > > > > 1950: Tarzan & the Slave Girl (Lex Baxter) > > 1951: Tarzan's Peril (Lex Baxter) > > 1952: Tarzan's Savage Fury (Lex Baxter) > > 1953: Tarzan & the She-Devil (Lex Baxter) > > 1955: Tarzan's Hidden Jungle (Gordon Scott) > > 1957: Tarzan & the Lost Safari (Gordon Scott) > > 1958: Tarzan & the Trappers (Gordon Scott) > > 1958: Tarzan's Fight for Life (Gordon Scott) > > 1959: Tarzan's Greatest Adventure (Gordon Scott) > > 1959: Tarzan the Ape Man (Gordon Scott) > > > > Look at the synopses of those movies. Maybe one of them will have > something familiar from the movie of interest. > > > > When you find the right one, or some possibilities for the right one, > check to find out if it's on YouTube. > > > > Michael Ossipoff > > > > > > > > > > On Sat, Jul 18, 2015 at 12:16 AM, sasch stephens > wrote: > > There is a Tarzan movie, maybe with Johnnie Weissmiller from the 1950's > which might have been
Re: Tarzan's sundial
When giving the Time-Altitude formula, I should also mention that sometimes its h answer should be reckoned with respect to north instead of south. Of course, during the negative-declination half of the year, the sun is always south of the east-west line, and h is always reckoned with respect to south. But, during the positive-declination half of the year, of course there's part of the day when the sun is north of the east-west line. At those times, the Time-Altitude formula's h answer is with respect to north instead of south. Of course that applies, likewise, to the Altitude-Watch approximation to Time-Altitude. So, when using those methods during the positive-declination half of the year, it's best to calculate or estimate when the sun will cross the east-west line. That's so, when the denominator of the Time formula for Az is zero. That's when: cos h = tan dec/tan lat. If you don't have a calculator nearby when you want that answer, you can approximate it by substituting dec and lat for their tangents. ...if the latitude is small, as it is where I reside, in Florida. I should mention that of course it's often more convenient to multiply by sec Alt than to divide by cos Alt. sec Alt can be estimated directly from the shadow-casting object and its shadow, or it can be gotten from tan Alt, which might be easier to measure, or easier to judge directly from the object and its shadow. Michael Ossipoff On Sun, Jul 19, 2015 at 2:57 PM, Michael Ossipoff wrote: > Barry-- > > Thanks for finding that scene! > -- > > Barry, Sasch & all-- > > Of course Tarzan’s sundial was more for measuring *duration*, rather than > time-of-day. > > > “Get out of the jungle before this duration is up!” > > > I once used a stick Azimuth Sundial for that same purpose, to measure a > duration for someone who didn’t have a watch: > > > My girlfriend at that time and I had been at the beach for some time, and > she was about to go to visit with a group of women who met daily at Carls’ > Junior fastfood restaurant. > > > There was some item at her house (I don’t remember what it was) that she > wanted to have with her when she left the beach. I offered to walk to her > place to find it, and bring it to her at the beach. But, in case I couldn’t > find it, I told her to go ahead and leave for the restaurant after a > certain duration. > > > She didn’t have a watch, and so I made a vertical-stick Azimuth Dial, on a > horizontally-smoothed area of sand, using a thin straight stick as the > gnomon. > > > I marked a small point in the sand, and told her that, if I haven’t > returned by the time the stick’s shadow reaches the mark, then to go ahead > and go to the restaurant meeting, because I couldn’t find the item. > > > I estimated how long it would take me to make the round-trip to her house, > and to find the item. > > > How I determined where to make the mark: > > > I determined it based on a solar direction-finding method that I’ve used > for a long time. I call it the “Altitude Watch Method” (AW), because it’s > an improvement on the familiar “Watch Method” (W), described in so many > books and articles. > > > AW is an approximation to the navigators’ “Time-Altitude Method” (TA). > > > TA says: > > > sin Az = sin h * (cos dec/cos Alt). > > > AW’s approximation consists of assuming that Az and h are > proportionally-related in the same way as sin Az and sin h. > > > At least some of the times when an Altitude Dial based on AW gives its > best estimates of the rate-of-change of Az are when the duration is short > enough so that the sun’s altitude doesn’t change a lot, and: > > > …1) h is small > > > Or > > > …2) the sun’s altitude and the magnitude of its declination are small. > > > But I tested the method, and found it to give good accuracy on the > occasions when I tested it. Maybe those occasions weren’t too far from > solar high noon, and that would explain the accurate results. > > > But, as an approximate measure of duration, where exact time-of-day isn’t > needed, the method should be satisfactory anytime. > > > Though I tested it a few times, I only actually *used* it on that one > occasion at the beach. > > > Michael Ossipoff > > 26N, 80W > > > > > > > > > > > > > > > > > > > On Sun, Jul 19, 2015 at 12:32 PM, Barry Wainwright wrote: > >> The film is the 1942 “Tarzan’s New York Adventure” and the scene is about >> 6 minutes in. >> >> I’ve uploaded a clip of the scene to You Tube, you can find it at &g
Time-Altitude method typo
Sorry, but there was a typo in my most recent post. I didn’t want to bother you with this, but I also didn’t want to leave the typo un-corrected. In the two paragraphs quoted below, in quotes, “h” should be replaced with “Az”: “Of course, during the negative-declination half of the year, the sun is always south of the east-west line, and h is always reckoned with respect to south. “But, during the positive-declination half of the year, of course there's part of the day when the sun is north of the east-west line. At those times, the Time-Altitude formula's h answer is with respect to north instead of south.” - --- At least as I use TA, both h and Az are always positive, whether they’re east or west of the north-south line. h has its usual meaning, reckoned from the meridian that crosses the south horizon-point, but Az is meant with respect to, measured from, south if the sun is south of the east-west line, and from north if the sun is north of the east-west line. In the northern hemisphere, in the north-declination half of the year, it would be necessary to know which side of the east-west line the sun is on. That is accomplished by calculating when the sun crosses the east west line. I’ll state that formula again: cos h = tan dec/tan lat. …evaluated (or estimated) once for any day when TA or AW will be used. As I said, I just didn’t want to leave the typo un-corrected. By the way, TA isn't very popular with navigators and surveyors, though they mention it, and maybe sometimes use it. That's because of the error-vulnerability introduced by the measurement of the altitude. And, when you're walking, or in a car, and don't have the opportunity to actually *measure* sec Alt or tan Alt, then that can make an error of a magnitude that matters some when hiking. But TA is simpler and briefer than the Time method (that's the familiar formula for azimuth, making use of time, latitude and declination) or the Altitude method (making use of altitude, latitude and declination), and lends itself to the convenient Altitude Watch method. Of course if you just want to know which direction is which, along a street, then you don't need great accuracy. Any determination is useful if you know or assume that it isn't off by 90 degrees (if, for example, all you need to know is which way on this street is south). Michael Ossipoff --- https://lists.uni-koeln.de/mailman/listinfo/sundial
Re: A translucent sundial
It sounds like the Translucent Flat Dials that I was discussing in an earlier post, maybe a month ago, give or take a few weeks. ...except that I was discussing _2-sided_ Translucent Flat Dials, with a gnomon on each side of the dial-plate, with the dial intended to be readable from both sides. Michael Ossipoff On Tue, Jul 28, 2015 at 7:06 AM, Thibaud Taudin Chabot wrote: > So it is actually the same as a window sundial but more or less in a > horizontal position and doesn't project its hourlines on a surface to read > time. > > At 12:47 28-7-2015, Robert Terwilliger wrote: > > If you hold your cursor to the right side of any image you will see a > carat "*>*" that will take you to the next photograph - and eventually to >  models for the construction. > > The time is read by looking up at the translucent ellipse as in this photo: > > http://photo.xuite.net/nycl.chiu/6138077/4.jpg > > Google translate also helps. > > Bob > > -- > > *From:* sundial [ mailto:sundial-boun...@uni-koeln.de > ] *On Behalf Of *Chi lian Chiu > *Sent:* Monday, July 27, 2015 1:51 AM > *To:* Sundial sundiallist > *Subject:* A translucent sundial > > ​Hi all, > > I am very glad to inform you that several pictures of the translucent > sundial up in the sky as I mentioned two years ago are now available at > > http://photo.xuite.net/nycl.chiu/6138077/1.jpg > > http://photo.xuite.net/nycl.chiu/6138077/2.jpg > > http://photo.xuite.net/nycl.chiu/6138077/3.jpg > > http://photo.xuite.net/nycl.chiu/6138077/4.jpg > > http://photo.xuite.net/nycl.chiu/6138077/5.jpg > > > > The dial is attached to a public art sculpture, “The Gate of Ecology†. > > name: The Sundial of Ecology > > type: sloped > > face plate material: 5 mm plus 8 mm double tempered glass > > face treatment: sandblasted to be translucent, leaving hour-lines > transparent > > hour numerals: marked on the frame, not on the face plate > > gnomon material: stainless steel, #304 > > inclination: 10 degrees due west (west end is the lower end) > > shape of the plate: oval, 1.8 m by 1.2 m > center height from the ground: 5.7 m > > location: 23.49N, 120.12E > > designer: Chi-Liang Chiu (individual) and Mega Design Co. > > funding source: Forestry Bureau, Council of Agriculture, Taiwan, Rep. of > China > > built date: Nov. 2013 > > > > Have a nice day! > > > > Chi-Liang > > 24.78N, 120.99E > --- > https://lists.uni-koeln.de/mailman/listinfo/sundial > > --- > https://lists.uni-koeln.de/mailman/listinfo/sundial > > > --- https://lists.uni-koeln.de/mailman/listinfo/sundial
Re: A translucent sundial
Accidentally omitted words: I meant to say, referring to the 2-sided Translucent Flat Dials, "...intended to be read from both sides, regardless of which side is illuminated." Michael Ossipoff On Tue, Jul 28, 2015 at 7:06 AM, Thibaud Taudin Chabot wrote: > So it is actually the same as a window sundial but more or less in a > horizontal position and doesn't project its hourlines on a surface to read > time. > > At 12:47 28-7-2015, Robert Terwilliger wrote: > > If you hold your cursor to the right side of any image you will see a > carat "*>*" that will take you to the next photograph - and eventually to >  models for the construction. > > The time is read by looking up at the translucent ellipse as in this photo: > > http://photo.xuite.net/nycl.chiu/6138077/4.jpg > > Google translate also helps. > > Bob > > -- > > *From:* sundial [ mailto:sundial-boun...@uni-koeln.de > ] *On Behalf Of *Chi lian Chiu > *Sent:* Monday, July 27, 2015 1:51 AM > *To:* Sundial sundiallist > *Subject:* A translucent sundial > > ​Hi all, > > I am very glad to inform you that several pictures of the translucent > sundial up in the sky as I mentioned two years ago are now available at > > http://photo.xuite.net/nycl.chiu/6138077/1.jpg > > http://photo.xuite.net/nycl.chiu/6138077/2.jpg > > http://photo.xuite.net/nycl.chiu/6138077/3.jpg > > http://photo.xuite.net/nycl.chiu/6138077/4.jpg > > http://photo.xuite.net/nycl.chiu/6138077/5.jpg > > > > The dial is attached to a public art sculpture, “The Gate of Ecology†. > > name: The Sundial of Ecology > > type: sloped > > face plate material: 5 mm plus 8 mm double tempered glass > > face treatment: sandblasted to be translucent, leaving hour-lines > transparent > > hour numerals: marked on the frame, not on the face plate > > gnomon material: stainless steel, #304 > > inclination: 10 degrees due west (west end is the lower end) > > shape of the plate: oval, 1.8 m by 1.2 m > center height from the ground: 5.7 m > > location: 23.49N, 120.12E > > designer: Chi-Liang Chiu (individual) and Mega Design Co. > > funding source: Forestry Bureau, Council of Agriculture, Taiwan, Rep. of > China > > built date: Nov. 2013 > > > > Have a nice day! > > > > Chi-Liang > > 24.78N, 120.99E > --- > https://lists.uni-koeln.de/mailman/listinfo/sundial > > --- > https://lists.uni-koeln.de/mailman/listinfo/sundial > > > --- https://lists.uni-koeln.de/mailman/listinfo/sundial
Re: Precision: the measure of all things
(I should clarify again that, for clarity, I like to capitalize _kinds_ of whatever sort of thing I'm talking about...such as kinds of sundials or hour-systems, though I realize that that capitalization is probably not officially correct.) Another closely-related interesting question is the matter of what _kind_ of hours are used. Of course every book or article on sundials points out that, before mechanical clocks became widespread, civil time was measured in "Temporary Hours", which divided the day, from sunrise to sunset, into 12 equal parts, and likewise divided the night, from sunset to sunrise, into 12 equal parts. Those books and articles nearly always imply or say that equal hours was a new invention when it was adopted--that someone invented a new way to designate time, and so it was adopted. Another frequent, and related, statement or implication is that the Horizontal Dial was an innovation that was came into use upon its invention because, before that, its possibility was there, but just hadn't occurred to anyone. But I read different. I read that Equal Hours were in use by astronomers and astrologers long before they were adopted for civil time, and so they were hardly a new invention at the time of their adoption for civil time. In fact, look at a Hemispherium or Hemicyclium. Designed to read in Temporary Hours, its hour-line, for a particular hour, crosses a different Equal-Hours line, according to the declination. Whether those Temporary Hours were drawn by calculation, or by empirical observation, it's plain that it would have been obvious to the dial-maker that he was making the 3 p.m. hour-line cross different Equal-Hours lines at different solar declinations. One thing that I'm objecting to is that many of those books imply that Temporary Hours are more primitive, and Equal Hours are something more advanced that therefore, when invented, immediately replaced Temporary Hours. Primitive? Rather, a lot more complicated and laborious to make. For sundials, and likewise for water-clocks. People should be impressed by the ingenuity and determination of early makers of sundials and water-clocks, who devised Temporary Hours markings and mechanisms for them. As for the Horizontal Dial, of course it's for Equal Hours. That's what it's convenient for. Sure, Flat Dials, including Horizontal Dials, and Polar Dials, and Equatorial Dials, and others, could have likewise been made for Temporary Hours, but they wouldn't have been easier to mark than a Hemicyclium. So it isn't surprising if the Horizontal Dial came into use around the same time as Equal Hours. What I read was that, though Equal Hours were well known and used by astronomers and astrologers, no one wanted them for civil timekeeping. Hence the effort and ingenuity used to devise Temporary Hours sundials and water-clocks. But, when the mechanical clock was invented, and came into relatively wide use (as tower-clocks, and in some homes), it was so much simpler to make clocks for Equal Hours, that, as a result, Equal Hours replaced Temporary Hours, for that reason of pure manufacturing-practicality. (By the way, were the early mechanical clocks, the Folliet Balance intertially-slowed clocks, without the fusee compensation, any more accurate than water-clocks, which were much cheaper and easier to build?) Temporary Hours surely made a lot of sense in agricultural societies, where it must have been very important and practical for farmers to know what percentage of the day remained. I don't advocate a return to Temporary Hours, because, speaking for myself, it seems to me that finding what percentage of the day is over, and how much or how little remains, seems a bit pessimistic, and maybe not a good way to name the time of day. ...but I realize that it had practical importance in agricultural societies. Michael Ossipoff On Mon, Jul 27, 2015 at 5:59 PM, Dan Uza wrote: > Hi everyone, > > If you haven't already, you might want to check out the first part of the > documentary "Precision: the measure of all things". It's about the > measurement of time and length, featuring the topic of sundials. There's an > interesting theory about how the day got split into 12 hours because this > number is highly divisible (but why not 60?). I just watched it on Da Vinci > Learning. > > Dan Uza > Romania > > --- > https://lists.uni-koeln.de/mailman/listinfo/sundial > > > --- https://lists.uni-koeln.de/mailman/listinfo/sundial
Re: Precision: the measure of all things
I should add: Didn't someone say that the oldest sundial known was a Chinese Equatorial Dial marked for Equal Hours? Anyway, in Europe, equal hours have been in use for, what, around 700 years? But, if I correctly remember what i read, Temporary Hours were in use in classical and ancient times, for more like 2700 years or more. On Mon, Jul 27, 2015 at 11:45 PM, Roger Bailey wrote: > Hi Dan, > > Don't worry, 60 is well represented in time and angular measurements. We > have 60 minutes in an hour, 60 seconds in a minute, 6 x 60 degrees in a > circle and again 60 minutes in a degree and sixty seconds in a minute. > Why? Being highly divisible is only part of the story. Other parts include > our year of 365.25 days, very close to 360 and six equilateral triangles in > a circle indicating that pi was close to 3 but greater as the arc is longer > that the cord. If a circle is 360, equilateral triangles are 60 and a > quadrant is 90. My preference for angular measurement is degrees and > decimal minutes as opposed to degrees, minutes seconds or decimal degrees, > From navigation experience, I recognize a minute of latitude is a nautical > mile. I can easily handle decimal miles. I hate grads using 100 rather that > 90 in a quadrant. Some French topo maps still use the Paris meridian for > longitude and grads for latitudes. This is as ridiculous as republican > time, 10 hours in a day, 100 minutes in a hour and 100 minutes in an hour. > Get over it as the French did with time. The Babylonians were onto > something when they defined our base 60 units of measurement. > > Regards, > Roger Bailey > > *From:* Dan Uza > *Sent:* Monday, July 27, 2015 2:59 PM > *To:* sundial@uni-koeln.de > *Subject:* Precision: the measure of all things > > Hi everyone, > > If you haven't already, you might want to check out the first part of the > documentary "Precision: the measure of all things". It's about the > measurement of time and length, featuring the topic of sundials. There's an > interesting theory about how the day got split into 12 hours because this > number is highly divisible (but why not 60?). I just watched it on Da Vinci > Learning. > > Dan Uza > Romania > > -- > > --- > https://lists.uni-koeln.de/mailman/listinfo/sundial > > -- > > No virus found in this message. > Checked by AVG - www.avg.com > Version: 2015.0.6081 / Virus Database: 4392/10318 - Release Date: 07/27/15 > > > --- > https://lists.uni-koeln.de/mailman/listinfo/sundial > > > --- https://lists.uni-koeln.de/mailman/listinfo/sundial
Re: Temporal Hours
Roger, thanks for the answer. Ok, I shouldn't say that as a fact without having more information than I do. This is what I was implying or saying, without really having much support for it: "In Europe and the fertile-crescent region, in ancient, classical and medieval times, before mechanical clocks (starting with Folliet-balance clocks) came into wide use, Equal Hours were of interest, for the most part, only to astronomers and astrologers. For ordinary civil timekeeping, for arranging meetings, keeping schedules or other civil/social purposes, Temporary Hours were preferred by pretty much everyone." Were a fair percentage of people making their appointments and schedules by Equal Hours in the times and places named in the above paragraph? I'm not being argumentative--I really don't know. -- Thanks for reminding me about Temporary Hours lines on Flat Dials being satisfactorily approximated by straight lines. I'd temporarily (no pun intended) forgotten that. It was a question that I'd asked, and received an answer to, when I first wrote to NASS. Were Flat-Dials (for Temporary or Equal Hours) in use before mechanical clocks were getting popular? What about _wide_ use? How early? - Can anyone explain why the early, inaccurate inertia-controlled Folliet-Balance clocks replaced the cheaper, more easily-made water-clocks? Were those earliest, most inaccurate mechanical clocks significantly, or any, more accurate than water-clocks? Michael Ossipoff On Tue, Jul 28, 2015 at 11:58 PM, Roger Bailey wrote: > Hi Michael and all, > > Temporal or Antique hours co-existed with equal hours from way back, > thousands of years. It didn't take a technological device like a clock to > cause a change. A more interesting point is the portrayal of temporal > hours, 12 unequal hours in the day on a flat sundial. It is easy on > Greek/Roman hemispheres but what about flat planar sundials. Is it > sufficient to calculate the points for the solstices and draw a straight > line between them? This works but is it right mathematically? To answer > this question, Fred Sawyer gave an excellent presentation on Antique Hours > at the NASS Conference in 2010 in Burlington. Was it really five years ago! > Here is a clip of the abstract from the NASS website. > > "Antique Hour Lines: Fred Sawyer gave another excellent example of his > reviews of the history of complex mathematical concepts for sundials. In > the case of Antique Hour Lines, the question was “Are they straight lines?” > For millennia they were assumed to be, but the assumption was questioned by > many mathematicians. Proofs were offered by Ibrahim Ibn Sinan in the 10th > century, Christopher Clavius in the 16th, Hellingweth in the 18th and many > including Montucla, Delambre and Cadell in the 19th, offering proofs that > the lines were in fact curved. The various proofs tended to be empirical > based on plotting the results of individual calculation. Biot offered an > analysis in 1841 and Davies in 1843, but the problem was not fully solved > until 1914 when Hugo Michnik studied the curves for the equatorial sundial, > providing a method to come up with non-parametric equations for the curve > for each hour. Fred then presented the graphs of various hour lines at > different latitudes and inclinations. The curves were amazingly complex > looking but the specific area of interest, where a shadow would be > projected was very close to the straight lines of the traditional method." > > This is why I belong to NASS, to read the Compendium and to go to the > conferences. Here we see solutions to problems we didn't even know existed. > > Regards, Roger Bailey > > *From:* Michael Ossipoff > *Sent:* Tuesday, July 28, 2015 4:47 PM > *To:* Dan Uza > *Cc:* sundial list > *Subject:* Re: Precision: the measure of all things > > > (I should clarify again that, for clarity, I like to capitalize _kinds_ of > whatever sort of thing I'm talking about...such as kinds of sundials or > hour-systems, though I realize that that capitalization is probably not > officially correct.) > > Another closely-related interesting question is the matter of what _kind_ > of hours are used. Of course every book or article on sundials points out > that, before mechanical clocks became widespread, civil time was measured > in "Temporary Hours", which divided the day, from sunrise to sunset, into > 12 equal parts, and likewise divided the night, from sunset to sunrise, > into 12 equal parts. > > Those books and articles nearly always imply or say that equal hours was a > new invention when it was adopted--that someone invented a new way to > designate time, and so it was adopted. Ano
Re: Temporal Hours
Hi Roger-- Thanks for the info. You answered my question about the first known Horizontal, Polar-Gnomon Dial. On Thu, Jul 30, 2015 at 12:26 AM, Roger Bailey wrote: > . Meeting for lunch was no problem. > ...unless you're using a portable Altitude Dial. I've long felt that that's a big disadvantage of Altitude Dials--their inaccuracy around noon, just the time when people would make lunch appointments. Michael Ossipoff --- https://lists.uni-koeln.de/mailman/listinfo/sundial
Re: due east
Hi Brent-- The paradox involves what you mean by "travel due east'. If you travel due east, and keep on traveling due east at every point of your journey, then you will indeed follow a parallel of latitude. If you were to drive your car in that fashion, always going due east, along a parallel of latitude, then your car's wheels and steering-wheel would have to be adjusted for a (slight) left-turn. ...as, for example, if you wanted to drive east along the U.S-Canadian border. But there's another thing that you could mean by traveling due east: But, if you set out due east, and then travel in a straight line, without letting your car's wheels curve your car left or right at all, then you're not following a parallel, and, you'd indeed end up going farther and farther south from your original latitude. As others have pointed out, a straight line on the Earth is also called a "great circle". So, the paradox was just the result of two different meanings of "travel due-east". Michael Ossipoff On Tue, Sep 15, 2015 at 10:10 AM, Brent wrote: > I'm confused maybe. > > I live in the northern hemishpere and anticipating the equinox on the 23rd. > > Supposedly the sun will rise due east. > > So if due east is a right angle from north south and I traveled due east I > would not follow my line of latitude. > I would get further and further south of my latitude the further I > traveled. > > So either the lines of latitude are not east west lines or due east is not > a straight line but curved. > I suspect lines of latitude are not east west lines? > They would work fine if the earth was not tilted, but it is. > > Wouldn't it make sense to coordinate the globe so lines of latitude (or > call them something else) are straight and a right angle > from north south? > > brent > > > > --- > https://lists.uni-koeln.de/mailman/listinfo/sundial > > > --- https://lists.uni-koeln.de/mailman/listinfo/sundial
Re: due east
Brent-- On Tue, Sep 15, 2015 at 7:47 PM, Brent wrote: > Michael; > > Ok, let's make it easier. > > On any day I want to stand in my backyard and look due east. > I don't want to travel anywhere. > > Do I look at where the sun will rise on the equinox or do I look slightly > to the left of that? (northern hemisphere) > You look at where the sun will rise on the equinox.. (but don't do it when the sun rises, because even if the rising or setting sun doesn't look very bright, due to mist or low altitude, the un-seen and un-felt infrared or UV could still do retinal-damage). > > If you tell me to look slightly to the left of where the sun will rise on > the equinox it would mean two things: > > 1. the sun doesn't rise due east on the equinox > 2. the east west line is not straight but curved > The equinox sun rises due east. But the east-west line is curved. But the curved-ness of the east-west line only matters if you want to travel on it. If you're, instead, just looking east, then, wherever you are, the direction you're looking is a straight line (a great circle). So, though you're looking due east, toward where the sun will rise, any places on the Earth that are in that line-of-sight will be slightly south of the parallel of latitude that you're on--even though they're due east from you. Their *direction* is due east. The *route* to them will soon have you going south of east instead of due east. So: Say the edge of a distant telephone-pole is due-east from you. Starting out toward it, you're starting out traveling due eastward. But, after you've proceeded even a little way, continuing in that same straight line toward the telephone-pole edge, you'll soon be traveling in a direction that's south of due east. Michael Ossipoff > > Thank you all for your replies. > brent > > > On 9/15/2015 4:00 PM, Michael Ossipoff wrote: > > Hi Brent-- > > The paradox involves what you mean by "travel due east'. > > If you travel due east, and keep on traveling due east at every point of > your journey, then you will indeed follow a parallel of latitude. > > If you were to drive your car in that fashion, always going due east, > along a parallel of latitude, then your car's wheels and steering-wheel > would have to be adjusted for a (slight) left-turn. ...as, for example, if > you wanted to drive east along the U.S-Canadian border. > > But there's another thing that you could mean by traveling due east: > > But, if you set out due east, and then travel in a straight line, without > letting your car's wheels curve your car left or right at all, then you're > not following a parallel, and, you'd indeed end up going farther and > farther south from your original latitude. > > As others have pointed out, a straight line on the Earth is also called a > "great circle". > > So, the paradox was just the result of two different meanings of "travel > due-east". > > Michael Ossipoff > > On Tue, Sep 15, 2015 at 10:10 AM, Brent wrote: > >> I'm confused maybe. >> >> I live in the northern hemishpere and anticipating the equinox on the >> 23rd. >> >> Supposedly the sun will rise due east. >> >> So if due east is a right angle from north south and I traveled due east >> I would not follow my line of latitude. >> I would get further and further south of my latitude the further I >> traveled. >> >> So either the lines of latitude are not east west lines or due east is >> not a straight line but curved. >> I suspect lines of latitude are not east west lines? >> They would work fine if the earth was not tilted, but it is. >> >> Wouldn't it make sense to coordinate the globe so lines of latitude (or >> call them something else) are straight and a right angle >> from north south? >> >> brent >> >> >> >> --- >> https://lists.uni-koeln.de/mailman/listinfo/sundial >> >> >> > > --- https://lists.uni-koeln.de/mailman/listinfo/sundial
Re: Possible sundial in movie
On Mon, Sep 28, 2015 at 3:24 PM, Dan-George Uza wrote: > Hello, > > Tonight I saw the trailer for "The 100-Year-Old Man Who Climbed Out the > Window and Disappeared". > > https://www.youtube.com/watch?v=P-k7DUQPHfQ > > After the old man climbs out the window at 0:53 he walks past what appears > to be a cast iron armillary sundial. However, as the equatorial band seems > to completely circle the globe I think this piece would not show time...at > least not around the equinoxes! > > Sure, some armillaries aren't sundials, but I'm sure that I've seen armillary sundials that had the equatorial band all the way around. IIf the band is of uniform width, then it won't tell time when the sun is *exactly* on the equator, but, even if the declination is the *least bit* non-zero, the gnomon will have a shadow on the hour-band. So I don't suppose that an armillary with an equatorial band would lose more than a few days of time-telling each year. Besides, maybe the upper part of the equatorial band is narrower than the lower part, as is sometimes the case. Michael Ossipoff > Speaking about sundials in movies, I found a useful list at the link below: > http://www.shadowspro.com/en/sundials-in-movies.html > > Best wishes, > > Dan Uza > > --- > https://lists.uni-koeln.de/mailman/listinfo/sundial > > > --- https://lists.uni-koeln.de/mailman/listinfo/sundial
Re: Romanian reclining sundial
On Thu, Oct 1, 2015 at 3:55 PM, Willy Leenders wrote: > A nice project for the decoration of the roof ! > Yes, but more than a decoration. > However, it is not possible to read the true local time. > Could you explain that statement? True local time, or true local time at the central-meridian, is what sundials are marked in. They used to typically give "temporary hours", but that is no longer their usual time-system. > And one can not deduce it for the place at longitude: 24° 30′ 3.82′′ E > (Bistrita) with only the table for EOTas a tool. > If the dial is marked in true-solar-time, as opposed to true-solar-time at the central meridian, and if the EoT table doesn't incorporate the longitude-correction, then one could get standard time by adding or subtracting 4 minutes from the EoT entry, for each degree of longitude west or east of the place's central meridian. Michael Ossipoff 26N, 80W On Sun, Oct 4, 2015 at 7:13 AM, Michael Ossipoff wrote: > > > On Thu, Oct 1, 2015 at 3:55 PM, Willy Leenders > wrote: > > >> A nice project for the decoration of the roof ! >> > > Yes, but more than a decoration. > > >> However, it is not possible to read the true local time. >> > > Could you explain that statement? > > True local time, or true local time at the central-meridian, is what > sundials are marked in. > > They used to typically give "temporary hours", but that is no longer their > usual time-system. > > > >> And one can not deduce it for the place at longitude: 24° 30′ 3.82′′ E >> (Bistrita) with only the table for EOTas a tool. >> > > If the dial is marked in true-solar-time, as opposed to true-solar-time at > the central meridian, and if the EoT table doesn't incorporate the > longitude-correction, then one could get standard time by adding or > subtracting 4 minutes from the EoT entry, for each degree of longitude west > or east of the place's central meridian. > > > > Michael Ossipoff > 26N, 80W > > --- >> https://lists.uni-koeln.de/mailman/listinfo/sundial >> >> >> > --- https://lists.uni-koeln.de/mailman/listinfo/sundial
Re: Romanian reclining sundial
On Fri, Oct 2, 2015 at 6:12 AM, Willy Leenders wrote: > Dan, > > What I mean is this: > > 1. > Together with the sundial on the roof is given the EOT table. > What can you do with it? > Well, you can add the EoT table entry to the time shown on the sundial, to get standard time. > As a result of the empirical way of construction on September 1 you can, > using the EOT table, determine the standard Eastern European Time on > other days. > On any day, yes. Of course, that's clear from what the original-poster said. > Specifying the length correction you could also determine the true local > time > Yes, you could get local true solar time by adding or subtracting 4 minutes to the sundial's reading for each degree of latitude east or west of the place's time-zone's central meridian. As for the choice of local true solar time, or true solar time at the central meridian, both dial-marking systems are frequently, widely, used. Which you use is a matter of individual preference. Either you mark the dial for true solar time at the central meridian, or you incorporate the longitude correction in the EoT table. Both methods are popular. > > 2. > To indicate the standard Eastern European Time you have many options: > clock, cell phone, computer ... > There's no need to a sundial. > Sundials have aesthetic value. Though they can often be of practical time-telling use, that isn't their only justification. Yes, a sundial marked in true solar time at the central meridian is, by implication, intended or emphasized for practical use. > Indicating the true local time is only possible on a sundial. > Let him do it ! > Yes, that's one valid preference, one vaild choice. But both choices are valid. Yes, I personally like a sundial to give local true solar time, and incorporate the longitude-correction in the EoT table. That's how I made my pocket-portable tablet-dials. Nevertheless it must be accepted that not everyone makes the same choice that we make, and that many sundials are marked in true solar time at the central meridian. Michael Ossipoff On Fri, Oct 2, 2015 at 6:12 AM, Willy Leenders wrote: > Dan, > > What I mean is this: > > 1. > Together with the sundial on the roof is given the EOT table. > What can you do with it? > As a result of the empirical way of construction on September 1 you can, > using the EOT table, determine the standard Eastern European Time on > other days. > Specifying the length correction you could also determine the true local > time > > 2. > To indicate the standard Eastern European Time you have many options: > clock, cell phone, computer ... > There's no need to a sundial. > Indicating the true local time is only possible on a sundial. > Let him do it ! > > > Willy Leenders > Hasselt in Flanders (Belgium) > > Visit my website about the sundials in the province of Limburg (Flanders) > with a section 'worth knowing about sundials' (mostly in Dutch): > http://www.wijzerweb.be > > > > > > > Op 1-okt-2015, om 22:06 heeft Dan-George Uza het volgende geschreven: > > Willy, > > I'm sorry but I did not quite understand your message. The dial is > supposed to show standard Eastern European Time, not true local time. The > longitude correction for Bistrita is already built in the hour marks > because they were empirically drawn according to the watch when EoT was 0. > Therefore the correction table only deals with variations in Eot. > > Dan > > On Thu, Oct 1, 2015 at 10:55 PM, Willy Leenders > wrote: > >> A nice project for the decoration of the roof ! >> However, it is not possible to read the true local time. >> And one can not deduce it for the place at longitude: 24° 30′ 3.82′′ E >> (Bistrita) with only the table for EOTas a tool. >> >> >> Willy Leenders >> Hasselt in Flanders (Belgium) >> >> Visit my website about the sundials in the province of Limburg (Flanders) >> with a section 'worth knowing about sundials' (mostly in Dutch): >> http://www.wijzerweb.be >> >> >> >> >> >> >> >> Op 1-okt-2015, om 21:24 heeft Dan-George Uza het volgende geschreven: >> >> Dear group, >> >> I am happy to be able to share a picture of the first Romanian reclining >> sundial built recently by Damaschin Berende, a friend from a neighboring >> town. It's made of plywood, it sits on a roof and it features both a EoT >> correction table and interchangeable hour marks for winter time and >> daylight saving time. Reported accuracy is so far around 1:30 min. >> Direction of gnomon across the roof was fixed by taking a plumb bob shadow &
Re: How wrong is your time zone: Map shows how far world clocks are from solar time
Here is the comment (with a few clarifications added) that I posted to Stefano's article: Stefano— I like the idea of that smart-clock dawn-based time. In the Roman and medieval world, “dawn” referred to the beginning of Civil Twilight, not to Sunrise, and that’s what I’d suggest. But I don’t think it’s necessary or desirable to go back to the old “Temporary Hours” that divided the sunrise to sunset period into 12 equal hours. Maybe start the day at Dawn, and use the current hour-length. While “Dawn” is the fully-arrived beginning of Civil Twilight, “Aurora” in Roman and medieval times, referred to the *beginning* of the arrival of Dawn. Whereas Civil Twilight conventionally begins when the Sun is 6 degrees below the horizontal, Aurora is when the Sun is about 9.37 degrees below the horizontal. I don’t notice any advantage of Swatch-Time over GMT (UTC). About your map-projection advocacy: Robinson’s looks good, for a non-elliptical map. But compare it to the elliptical maps, Hammer, Aitoff, Mollweide and Apianus II. The 1st 3 of those are equal-area, and even Apianus II gives more accurate areas than Robinson. The ellipticals have a more realistic and accurate globular shape than Robinson. Their pole is accurately a point rather than a line. Their meridians accurately converge at that point. What, exactly, is Robinson’s advantage over the ellipticals? Robinson's popularity is largely a matter of current fashion. Robinson has one property: It’s pseudocylindrical. Better put, it’s *cylindroid*. A map is cylindroid if it’s cylindrical or pseudocylindrical. (A map is cylindroid if its parallels are straight horizontal parallel lines, each uniformly divided (uniform scale) along its length.) Why settle for just that one property?? Mollweide and Apianus II are cylindroid too. But Mollweide is equal-area, and Apianus II is linear (Y co-ordinate is linear with latitude and X co-ordinate is linear with longitude). There are many equal-area cylindroid maps. There is a variety of linear cylindroid maps, including Apianus II, Eckert III, and Cylindrical Equidistant. So there’s no need to settle for Robinson’s having only the cylindroid property. Why not have equal-area or linearity as well? …and combined with globular realism. But yes, as you said, a cylindrical map is more convenient for what you were doing. As for that website you linked to, with the line-drawings and comments about a few map projections, the author of that didn’t even mention any elliptical projections. And, basically, he was just expressing his allegiance to current fashion. Michael Ossipoff On Sat, Oct 24, 2015 at 6:22 PM, Dan-George Uza wrote: > > http://www.slate.com/blogs/the_world_/2014/02/21/how_wrong_is_your_time_zone_map_shows_how_far_ahead_or_behind_the_world.html > > Are you aware of any territories following official solar time? > > Dan Uza > > --- > https://lists.uni-koeln.de/mailman/listinfo/sundial > > > --- https://lists.uni-koeln.de/mailman/listinfo/sundial
Re: How wrong is your time zone: Map shows how far world clocks are from solar time
Minor correction to what I just posted: The Aitoff projection *isn'*t equal-area (but it's nearly so). Aitoff, was introduced in the late 1880s. Hammer was introduced just a few years later. Hammer acknowledged that his map is just an equal-area version using Aitoff's construction-principle, and Hammer's projection is often called "Hammer-Aitoff". Hammer and Aitoff arguably look more realistic than Mollweide and Apianus II, but Hammer and Aitoff aren't cylindroid. Hammer has only the equal-area property, and Aitoff doen't have a property. Incidentally, Mollweide was introduced in 1805, by a teacher in Germany, and has been very popular. Michael Ossipoff On Sun, Oct 25, 2015 at 4:44 AM, Fabio nonvedolora < fabio.sav...@nonvedolora.it> wrote: > hi, I applied the same map on the globe. > [image: globe-Europe-400] > > ciao Fabio > > PS on request I can send other views with more pixels > > Fabio Savian > fabio.sav...@nonvedolora.it > www.nonvedolora.eu > Paderno Dugnano, Milano, Italy > 45° 34' 10'' N, 9° 10' 9'' E, GMT+1 (DST +2) > > --- > https://lists.uni-koeln.de/mailman/listinfo/sundial > > > --- https://lists.uni-koeln.de/mailman/listinfo/sundial
Re: Southern Hemisphere
People who have already replied have said pretty much everything that I'd have said. As several people pointed out, yes the shadow-casting gnomon-edge should be tipped 32 degrees above the horizonal, at latitude 32 south. But, because it's south latitude, the up-pointing end of the gnomon should point southward, as was also pointed out. ...and the hour-marking should be anti-clockwise instead of clockwise, because the sun goes around the sky anti-clockwise in the Southern Hemisphere. Of course the reason why your analog clocks and watches have clockwise dials is because the sun goes around clockwise in the Northern Hemisphere. Someone pointed out that an Equatorial Band Sundial works fine at or near the equator. A Horizontal Flat Dial also works at the equator. But it takes the form of a Polar Dial, and, because it's a Polar Dial, its range of timetelling hour is limited. A Horizontal Flat Dial would work fine at the North Pole or South Pole. There, it would be an Equatorial-Dial. But it wouldn't tell time in winter (more accurately, any time when the declination is south). ...but there wouldn't be sunlight there, when declination is south, anyway, and so no sundial would tell time then. Michael Ossipoff 26N, 80W On Sun, Nov 15, 2015 at 5:37 PM, Phil Dorman wrote: > Hi Everyone, > > > > I joined this list because I have a specific question which I can’t find a > definitive answer to. > > > > I want to install a sundial at Perth WA Australia which is pretty close to > 32deg South latitude. > > From what I can determine that means the Gnomon should be 32deg above > horizontal. > > Or is that just for the Northern Hemisphere ?? > > > > As I move North in Australia the Latitude number gets Smaller > > Eg Latitude of Brisbane QLD (further North) is 27.46deg > > So presumably the Latitude at the Equator would be Zero ! > > Which would mean a sundial Gnomon at the Equator would be Horizontal ie > Flat on the Ground > > Which of course would not work. > > And at the South Pole it would be Vertical 90deg from Horizontal and also > would not work since there would be no ground for the shadow to fall on. > > > > So. Am I correct to put it at 32deg from Horizontal for Perth WA or not ? > > > > Phil Dorman /:~)> > > [image: MAATES_Transparent_for_email] <http://www.maates.com/> > > > *Machinery Appreciation & Transport Engineering Society*946 Wattagan Crk > Rd > Watagan NSW 2325 > > 0419 501285 > > > > > > --- > https://lists.uni-koeln.de/mailman/listinfo/sundial > > > --- https://lists.uni-koeln.de/mailman/listinfo/sundial
Re: Southern Hemisphere
Oops, a typo: I meant to say that, at the North Pole, no sundial will tell time when the solar declination is south. But, of course, at the South Pole, it's when the solar declination is *north*, that there won't be sunshine and sundials won't tell time. Michael Ossipoff On Mon, Nov 16, 2015 at 1:25 PM, Michael Ossipoff wrote: > People who have already replied have said pretty much everything that I'd > have said. > > As several people pointed out, yes the shadow-casting gnomon-edge should > be tipped 32 degrees above the horizonal, at latitude 32 south. > > But, because it's south latitude, the up-pointing end of the gnomon should > point southward, as was also pointed out. ...and the hour-marking should > be anti-clockwise instead of clockwise, because the sun goes around the sky > anti-clockwise in the Southern Hemisphere. > > Of course the reason why your analog clocks and watches have clockwise > dials is because the sun goes around clockwise in the Northern Hemisphere. > > Someone pointed out that an Equatorial Band Sundial works fine at or near > the equator. A Horizontal Flat Dial also works at the equator. But it takes > the form of a Polar Dial, and, because it's a Polar Dial, its range of > timetelling hour is limited. > > A Horizontal Flat Dial would work fine at the North Pole or South Pole. > There, it would be an Equatorial-Dial. But it wouldn't tell time in winter > (more accurately, any time when the declination is south). ...but there > wouldn't be sunlight there, when declination is south, anyway, and so no > sundial would tell time then. > > Michael Ossipoff > 26N, 80W > > On Sun, Nov 15, 2015 at 5:37 PM, Phil Dorman wrote: > >> Hi Everyone, >> >> >> >> I joined this list because I have a specific question which I can’t find >> a definitive answer to. >> >> >> >> I want to install a sundial at Perth WA Australia which is pretty close >> to 32deg South latitude. >> >> From what I can determine that means the Gnomon should be 32deg above >> horizontal. >> >> Or is that just for the Northern Hemisphere ?? >> >> >> >> As I move North in Australia the Latitude number gets Smaller >> >> Eg Latitude of Brisbane QLD (further North) is 27.46deg >> >> So presumably the Latitude at the Equator would be Zero ! >> >> Which would mean a sundial Gnomon at the Equator would be Horizontal ie >> Flat on the Ground >> >> Which of course would not work. >> >> And at the South Pole it would be Vertical 90deg from Horizontal and also >> would not work since there would be no ground for the shadow to fall on. >> >> >> >> So. Am I correct to put it at 32deg from Horizontal for Perth WA or not ? >> >> >> >> Phil Dorman /:~)> >> >> [image: MAATES_Transparent_for_email] <http://www.maates.com/> >> >> >> *Machinery Appreciation & Transport Engineering Society*946 Wattagan Crk >> Rd >> Watagan NSW 2325 >> >> 0419 501285 >> >> >> >> >> >> --- >> https://lists.uni-koeln.de/mailman/listinfo/sundial >> >> >> > --- https://lists.uni-koeln.de/mailman/listinfo/sundial
Re: Just the right spot and time!
The photographer must chosen in advance to take such a picture, and chosen the right time for the picture. Michael Ossipoff On Tue, Dec 1, 2015 at 9:11 AM, Dave Bell wrote: > Yes, the surprise is not so much that it happened, but that the > photographer was there at the one(?) precise date and time. > > Like a stopped clock, it’s precisely correct, once each period! > > Makes a great picture, regardless. > > > > Dave > > > -- > > *From:* sundial [mailto:sundial-boun...@uni-koeln.de] *On Behalf Of *Jackie > Jones > *Sent:* Tuesday, December 01, 2015 4:48 AM > *To:* 'Dan-George Uza'; sundial@uni-koeln.de > *Subject:* RE: Just the right spot and time! > > > > I would have thought it should be very simple and not a freak. As long as > the sides of the post are parallel to the paving slabs and the sun is > exactly south (or north if you are in the southern hemisphere), at twice a > year this should be the result. The dates would depend on the height of > the post. Although, I think it should work even if it isn’t due south, > just when the sun is directly behind the post and the right height. > > Jackie > > > > Jackie Jones > > 50° 50’ 09” N0° 07’ 40” W > > > > > > > > > > > > *From:* sundial [mailto:sundial-boun...@uni-koeln.de] *On Behalf Of > *Dan-George > Uza > *Sent:* 01 December 2015 11:36 > *To:* sundial@uni-koeln.de > *Subject:* Just the right spot and time! > > > > Hello, > > > > This freak shadow alignment is featured on ASAP Science's Facebook page. > The question is how to design something similar. Anybody? > > > > Dan Uza > > > > --- > https://lists.uni-koeln.de/mailman/listinfo/sundial > > > --- https://lists.uni-koeln.de/mailman/listinfo/sundial
Re: dodecahedron
That's interesting, and I've intended to eventually make a dodecahadral sundial. But just for decoration. A dodecahedral's faces are too small (for a given overall dial-size) for it to be a practical choice for a distant-readable sundial. Of course a cubic dial's faces are as big across as the whole cube is. Michael Ossipoff On Tue, Jan 5, 2016 at 11:46 PM, Roger Bailey wrote: > Thanks Fabio and Riccardo, > > This is really cool. It makes the design so easy, that it almost feels > like cheating. Consider the classic painting by Holbein of Kratzer working > on a simpler polyhedron and not getting it right. See > https://www.oneonta.edu/faculty/farberas/arth/Images/Ambassadors/holbein_kratzer_polyhed.jpg > > > Regards, Roger Bailey > > > *From:* Fabio nonvedolora > *Sent:* Tuesday, January 05, 2016 7:59 AM > *To:* sundial@uni-koeln.de > *Subject:* dodecahedron > > Hi all > > Riccardo Anselmi, an italian gnomonist, uploaded a new paper sundial, the > app 47 (www.sundialatlas.eu/atlas.php?app=47), it is a dodecahedron > inspired to a sundial in Palermo, Sicily, IT619. > > Enjoy it, ciao Fabio > > Fabio Savian > fabio.sav...@nonvedolora.it > www.nonvedolora.eu > Paderno Dugnano, Milano, Italy > 45° 34' 10'' N, 9° 10' 9'' E, GMT+1 (DST +2) > > -- > > --- > https://lists.uni-koeln.de/mailman/listinfo/sundial > > -- > > No virus found in this message. > Checked by AVG - www.avg.com > Version: 2016.0.7294 / Virus Database: 4489/11323 - Release Date: 01/04/16 > > > --- > https://lists.uni-koeln.de/mailman/listinfo/sundial > > > --- https://lists.uni-koeln.de/mailman/listinfo/sundial
Re: It's still summer in Sydney (or is it?)
On Sun, Mar 6, 2016 at 2:52 PM, John Pickard wrote: > Good morning all (and especially those in the Northern Hemisphere still > stuck in winter), > > The following letter appeared in the Sydney Morning Herald (Saturday 5 > March 2016, p. 39) > > "Still summer in Sydney. > > It's hard not to be amused by the apparently genuine surprise expressed > this past week - mainly by television weather presenters - at the high > temperatures being recorded around the country 'in the first week of > autumn'. I'm not sure which authority declared that autumn starts on March 1 In the U.S., our astronomers have proclaimed that summer begins with the summer solstice, and that spring begins wit the spring equinox. ...proclaimed with absolutely no justification. It's become our national definition of the seasons. I guess anything can mean anything if you define it that way. But, obvious to everyone (other than our astronomers and the newscasters who parrot them), by the time June 21 arrives, it has been summer for a long time. It would be much more in keeping with our experience with the seasons to say that Summer begins when June begins. ...and guess what? That's what they say in Australia. Australia doesn't share our ridiculous notion of starting the seasons on the solstices and equinoxes. In Australia, it's understood that Summer begins when December begins, and that Winter begins when June begins. But evidently it's still assumed that there are 4 seasons of equal length. Here in the U.S., it's obvious that March isn't spring. Yes, there are often _a few_ occasional indications that spring is approaching. But, realistically, March would be better included in Winter, if we insist on 4 seasons. Likewise, September tends to be a very summer-like. If we must have 4 months, then it would be less inaccurate to say that winter is December, January, February and March. ...and that summer is June, July, August and September. Spring is April and May. Autumn is October and November. But, more realistically, because March can have _a few_ days that somewhat preview spring (maybe with floral scents), March might better be called "Pre-Spring". Likewise, September might be better-called "Pre-Autumn"., because there does begin to be a bit of cooling later in September. So, instead of 4 seasons, there are 6. ...with March and September being 1-month seasons. The notion of 6 seasons isn't new. It's been proposed by people who specialize in these matters. > ; however the change of seasons is an immutable astronomical event... Incorrect. The seasons of course result from astronomical causes, but they aren't validly defined by astronomical events, such as equinoxes and solstices. > resulting from a shift in the earth's axis each three months on the two > equinoxes and the two solstices, which coincide with the human invented > calendar dates of (approximately) March and September 21; and June and > December 21. Human-invented yes. U.S. astronomer-invented (and media broadcaster parroted). So it has not been an amazingly hot start to "autumn'; it is still summer > and will be for nearly three more weeks. > Of course. If you're going to define 4 seasons, then March is part of Southern Hemisphere summer. December through March. But it would make even more sense to speak of March and September as 1-month seasons, as described above. Michael Ossipoff --- https://lists.uni-koeln.de/mailman/listinfo/sundial --- https://lists.uni-koeln.de/mailman/listinfo/sundial
Re: First sundials
I've read that there's evidence that the first accurate & precise timetelling sundials were in China. Stone disks, marked like equatorial sundials, with a hole in the center that could be for a gnomon were found in China, dating to a time that's earlier than other sundials that have beenfound. Equatorial disk sundials supported by the disk and by the end of the gnomon on the ground are still in use. Michael Ossipoff On Thu, Nov 24, 2016 at 4:15 AM, Darek Oczki wrote: > Dear all > > I would like to ask your opinion on the first sundials which inspired > gnomonic inventions developed through following centuries. In all > literature available in my country it is repeated that the first dials were > sticks set upright on sent or big trees and rocks casting shadow on earth. > This allowed the first men to observe the shadow motions throughout the > day. Well, I guess it is a way to describe the beggining.. yet it does not > satisfy me - sounds pretty boring :) > > Considering the scaphe and other hemispheric dials of Greece there seems > to be a vast gap between the above concept and those very sophisticated > dials. Does any of the group members have any other perspective on how it > all could really begin? (apart from any alien intervention theory). > > -- > Best regards > Darek Oczki > 52N 21E > Warsaw, Poland > GNOMONIKA.pl > Sundials in Poland > http://gnomonika.pl > > > --- > https://lists.uni-koeln.de/mailman/listinfo/sundial > > > --- https://lists.uni-koeln.de/mailman/listinfo/sundial
Re: Precise locations
Two things that I ask someone to explain: 1. How does the 3-word position-designation work? Aside from the names of the positions, what is the co-ordinate system? Latitude & longitude? How are the 3 words chosen for each of the 3 meter by 3-meter locations? 2. What's wrong with latitude & longitude? ...or, if preferred, some widely-used plane-coordinate system? Michael Ossipoff On Sun, Oct 16, 2016 at 1:35 PM, Ian Maddocks wrote: > Hi Doug > > If you haven't been concentrating I added the W3W address to my signature > a few months back. > Given the 3 m resolution you actually get a few choices of what address to > pick for any given plot of land. frog.happy.froze is actually more my > living room than front door. I wandered the cursor around till I found > the most memorable three words > > At the moment if you want to navigate by W3W the NavMii free mobile sat > nav app (using OpenStreetMap data) understands the addresses. > https://play.google.com/store/apps/details?id=com.navfree.android.OSM.ALL > in the descriptions says "*Local Place search (powered by TripAdvisor, > Foursquare and What3Words)"* > > The other site that uses them is www.streetmap.co.uk.For those of us > dial recorders who want to have a location converted to multiple formats as > easily as possible the "Click here to convert coordinates" under the maps > is invaluable, and includes the W3W reference on the last line see > http://www.streetmap.co.uk/idgc.srf?x=538955&y=177217 for example > > Ian > > Ian Maddocks > Chester, UK > 53°11'50"N 2°52'41"W > frog.happy.froze > > > > -- > *From:* sundial on behalf of Douglas > Bateman > *Sent:* 16 October 2016 15:58 > *To:* Sundial list > *Subject:* Re: Precise locations > > I have been told of another method called what3words.com > > Designed in 2013 and developed since then, it uses a grid of the world > made up of 57 trillion squares of 3 metres by 3 metres. Each square has > been given a 3-word address. what3words has named the 17 trillion squares > on land with 3 words in 10 other languages in addition to English. Of > potential value to less developed countries. My contact says: "A very > good idea I think as it is easier than numbers and covers the whole globe > (dependent of course on the w3w database continuing to exist, which let's > hope it does) to give e.g. addresses in African shanty towns or remote > villages in India as well as where there are postcodes." > > An intriguing system, based on the fact that three words, however > unrelated, are rather more memorable than a latitude/longitude. Typing > Greenwich Observatory comes up with oval.blast.improving. My house has a > similar unique set of words. > > Well worth a look. > > Doug > > On 16 Oct 2016, at 11:39, Martina Addiscott > wrote: > > In message > Douglas Bateman wrote: > > Sundiallers like to give precise locations for dials, but (a little > off-list) I have a bottle of Campo Viejo Rioja 2014 wine in front of me > which gives at the top of the label N 42º 28’ 48†W 02º 29’ 08†. > Although in a small font it is clearly printed above the brand name. > > Google Earth shows a large vineyard, and indeed the brand, at this > location. > > This is a new one on me, and I wonder how many products are giving their > source location in geographical coordinates. > > Open for discussion! > > Doug > --- > https://lists.uni-koeln.de/mailman/listinfo/sundial > > > > As far as physical 'products' are concerned, these days they would > probably have a "QRcode" - you know, one of those small square blocks > which just seem to contain a 'jumble' of black and white pixels. > > Those are mainly used to direct people straight to a website, but > they can contain a lot more information (if you needed to do so). > > > If you want to include an actual geographical location, then one of > the best ways is to use a "NAC code" - which stands for 'Natural Area > Coding' also known as Universal Map Coding, or a Universal Address). > > It is usually included as a 'meta', within any website design coding. > > > For sundial-related subjects, the only people I know that use these > methods are "Modern Sunclocks" - and (if anyone is interested), I > have 'attached' the QRcode they use to drive people to their website. > > Within the 'meta' code of that website they also display a NAC code, > so that any people can find-out their exact Latitude and Longitude. > > > Sincerely, > > Martina Addiscott > > > > -- > > --- > https://lists.uni-koeln.de/mailman/listinfo/sundial > > > > --- > https://lists.uni-koeln.de/mailman/listinfo/sundial > > > --- https://lists.uni-koeln.de/mailman/listinfo/sundial
Re: Precise locations
Ian-- Thanks for the explanation. That answers both of my questions. Easier to remember, and less-likely for someone to mis-write one of the characters. I can see where there are applications where those qualities would be helpful. A lot of houses & cottages already have names, and so wouldn't it be good for people to be able to request that the square containing their front-door have the name of their house, if that word-combination (or something too close to it) isn't already in use? Thanks again. Michael Ossipoff On Mon, Dec 26, 2016 at 3:15 PM, Ian Maddocks wrote: > Hi Michael > > From reading the web site, as I understand it, they have chosen the words > from a big dictionary file. The interesting points were that they > deliberately choose smaller words for built up areas, going to larger words > elsewhere on landmass and the biggest words out to sea. This was to make > the most likely to be used combinations shorter and more memorable. They > also filtered out all the rude words. They have also taken the trouble to > ensure that similar groups of words are no where near each other. If you > try hovering over the map and looking at each square the words from one > square to the next are quite different. If you go to their map and type in > two or two and a half words till the suggestions come up you will see that > similar suggestions (maybe one ends in a plural) are nowhere near each > other to make typos obvious. Another feature is that different languages > are not just translations of the base English, in case words are longer or > more easily confused on the other languages. I haven't seen what grid the > system is based on ,though i presume standard 1984 Sat nav. > > Why? Will their main aim was to give accurate easy mapping to places > without road names or post codes. Even our post codes are only accurate to > 100 m or so but the situation is worse in less developed places. If you > live in an over crowded place you can still give an accurate address really > easily. If your delivery driver was using free open source map from > Navmii (sp?) , formerly Open Street Map he should be able to find you to > 3m. It's free mapping on your phone that understands w3w. Also the web > site streetmap.co uk does. > This is their target market. They don't expect you to radio the coast > guard with your coordinates in this format! > > It's more accurate than a post code , and easy to remember compared to lat > and long to the same accuracy. > > Merry Christmas > > Ian > Chester, UK > > Get Outlook for Android <https://aka.ms/ghei36> > > From: Michael Ossipoff > Sent: 7:34PM, Monday, 26 December > Subject: Re: Precise locations > To: Ian Maddocks > Cc: Douglas Bateman, Sundial list > > Two things that I ask someone to explain: > > 1. How does the 3-word position-designation work? Aside from the names of > the positions, what is the co-ordinate system? Latitude & longitude? How > are the 3 words chosen for each of the 3 meter by 3-meter locations? > > 2. What's wrong with latitude & longitude? > > ...or, if preferred, some widely-used plane-coordinate system? > > Michael Ossipoff > > On Sun, Oct 16, 2016 at 1:35 PM, Ian Maddocks > wrote: > > Hi Doug > > If you haven't been concentrating I added the W3W address to my signature > a few months back. > > Given the 3 m resolution you actually get a few choices of what address to > pick for any given plot of land. frog.happy.froze is actually more my > living room than front door. I wandered the cursor around till I found > the most memorable three words > > At the moment if you want to navigate by W3W the NavMii free mobile sat > nav app (using OpenStreetMap data) understands the addresses. > > https://play.google.com/store/apps/details?id=com.navfree.android.OSM.ALL > > in the descriptions says "*Local Place search (powered by TripAdvisor, > Foursquare and What3Words)"* > > The other site that uses them is www.streetmap.co.uk.For those of us > dial recorders who want to have a location converted to multiple formats as > easily as possible the "Click here to convert coordinates" under the maps > is invaluable, and includes the W3W reference on the last line see > http://www.streetmap.co.uk/idgc.srf?x=538955&y=177217 for example > > Ian > > Ian Maddocks > Chester, UK > 53°11'50"N 2°52'41"W > frog.happy.froze > > > *From:* sundial on behalf of Douglas > Bateman > *Sent:* 16 October 2016 15:58 > *To:* Sundial list > *Subject:* Re: Precise locations > > > > I have been told of another method called what3words.com > > Desi
Re:
1. I don't understand how a spreadsheet's rectangularly-arranged table of values is a problem for designing circular things. The values calculated and saved in that table can represent polar co-ordinates as well as anything else. 2. But here is *my* question that motivates this reply: Is it possible (without purchasing or downloading additional software) to print out graphics from Excel? ...to calculate, in Excel, co-ordinates of points along some curve, and then print-out the curve? ...useful for drawing a map, or a sundial, or any of lots of other things. Michael Ossipoff 2017-01-20 12:26 GMT-05:00 graham stapleton via sundial < sundial@uni-koeln.de>: > Diese Nachricht wurde eingewickelt um DMARC-kompatibel zu sein. Die > eigentliche Nachricht steht dadurch in einem Anhang. > > This message was wrapped to be DMARC compliant. The actual message > text is therefore in an attachment. > > -- Forwarded message -- > From: graham stapleton > To: "sundial@uni-koeln.de" > Cc: > Date: Fri, 20 Jan 2017 17:26:06 + (UTC) > Subject: Circular Spreadsheet Software > Is there any freeware (or at least inexpensive software) that can do in a > circle that which Excel does in a quadilateral? Apart from variable > numbers of radii and concentric circles, numbers and text need to appear in > the circles. I've found something that does the first part, (albeit PDF) > but not the latter. Thank you. > > --- > https://lists.uni-koeln.de/mailman/listinfo/sundial > > > --- https://lists.uni-koeln.de/mailman/listinfo/sundial
Re:
I mean, just using Excel, without using VBA. Michael Ossipoff On Sun, Jan 22, 2017 at 11:45 AM, Michael Ossipoff wrote: > 1. I don't understand how a spreadsheet's rectangularly-arranged table of > values is a problem for designing circular things. The values calculated > and saved in that table can represent polar co-ordinates as well as > anything else. > > 2. But here is *my* question that motivates this reply: > > Is it possible (without purchasing or downloading additional software) to > print out graphics from Excel? ...to calculate, in Excel, co-ordinates of > points along some curve, and then print-out the curve? > > ...useful for drawing a map, or a sundial, or any of lots of other things. > > Michael Ossipoff > > 2017-01-20 12:26 GMT-05:00 graham stapleton via sundial < > sundial@uni-koeln.de>: > >> Diese Nachricht wurde eingewickelt um DMARC-kompatibel zu sein. Die >> eigentliche Nachricht steht dadurch in einem Anhang. >> >> This message was wrapped to be DMARC compliant. The actual message >> text is therefore in an attachment. >> >> -- Forwarded message -- >> From: graham stapleton >> To: "sundial@uni-koeln.de" >> Cc: >> Date: Fri, 20 Jan 2017 17:26:06 + (UTC) >> Subject: Circular Spreadsheet Software >> Is there any freeware (or at least inexpensive software) that can do in a >> circle that which Excel does in a quadilateral? Apart from variable >> numbers of radii and concentric circles, numbers and text need to appear in >> the circles. I've found something that does the first part, (albeit PDF) >> but not the latter. Thank you. >> >> --- >> https://lists.uni-koeln.de/mailman/listinfo/sundial >> >> >> > --- https://lists.uni-koeln.de/mailman/listinfo/sundial
Re: Re:
Simon-- Thanks for the answer to my question. I was hoping that Excel had that capability. I'll give it a try. On Sun, Jan 22, 2017 at 12:08 PM, illustratingshad...@gmail.com < illustratingshad...@gmail.com> wrote: > Yes, please download. > > illustratingshadows.xls > > from Illustrating Shadows <http://www.illustratingshadows.com> > > and look at some of the subsheets. Use the insert chart feature in excel. > Look at my h-dial-analemma worksheet which uses Cartesian coordinates > creating the familiar figure of 8. > > Warning... aspect ratio is not preserved, that is why I also add two > orthogonal lines as in "h dial" worksheet, so you can stretch or squeeze > the chart until the lines intersect at 90 degrees. > > My web also has notes on messing with excel. > > Also consider Kingsoft. > > Caution with open office however because I once got malware from the > official site, not detected by the virus checker I used back then, which > was a top of the line. > > Simon > > www illustratingshadows . com > > > > > Sent from Yahoo Mail on Android > <https://overview.mail.yahoo.com/mobile/?.src=Android> > > On Sun, Jan 22, 2017 at 9:46, Michael Ossipoff > wrote: > I mean, just using Excel, without using VBA. > > Michael Ossipoff > > On Sun, Jan 22, 2017 at 11:45 AM, Michael Ossipoff > wrote: > >> 1. I don't understand how a spreadsheet's rectangularly-arranged table of >> values is a problem for designing circular things. The values calculated >> and saved in that table can represent polar co-ordinates as well as >> anything else. >> >> 2. But here is *my* question that motivates this reply: >> >> Is it possible (without purchasing or downloading additional software) to >> print out graphics from Excel? ...to calculate, in Excel, co-ordinates of >> points along some curve, and then print-out the curve? >> >> ...useful for drawing a map, or a sundial, or any of lots of other things. >> >> Michael Ossipoff >> >> 2017-01-20 12:26 GMT-05:00 graham stapleton via sundial < >> sundial@uni-koeln.de>: >> >>> Diese Nachricht wurde eingewickelt um DMARC-kompatibel zu sein. Die >>> eigentliche Nachricht steht dadurch in einem Anhang. >>> >>> This message was wrapped to be DMARC compliant. The actual message >>> text is therefore in an attachment. >>> >>> -- Forwarded message -- >>> From: graham stapleton >>> To: "sundial@uni-koeln.de" >>> Cc: >>> Date: Fri, 20 Jan 2017 17:26:06 + (UTC) >>> Subject: Circular Spreadsheet Software >>> Is there any freeware (or at least inexpensive software) that can do in >>> a circle that which Excel does in a quadilateral? Apart from variable >>> numbers of radii and concentric circles, numbers and text need to appear in >>> the circles. I've found something that does the first part, (albeit PDF) >>> but not the latter. Thank you. >>> >>> -- - >>> https://lists.uni-koeln.de/mai lman/listinfo/sundial >>> <https://lists.uni-koeln.de/mailman/listinfo/sundial> >>> >>> >>> >> > Links in the message > Illustrating Shadows <http://www.illustratingshadows.com> > --- https://lists.uni-koeln.de/mailman/listinfo/sundial
Re: Why we should reform the Calendar
stem is an improvement over our current Roman months, because the months are much more uniform. That allows much meaningful & accurate monthly statistics. But suppose you want something more radical (as is Gorman's 28X13 system): In that case, just don't have months, because their continuity & familiarity purpose would be lost anyway. Use the WeekDate system. No months. Weeks are numbered. Here's today's date in the (currently internationally widely-used) ISO WeekDate calendar: 4 Saturday That means Saturday of the 4th week. Actually, because not all countries and languages call the da ys of the week by the same names, here is how the ISO (International Standards Organization) words today's date. 2017W046 The "W" indicates that the WeekDate system is being used. The "04" denotes the 4th week. The "6" denotes the 6th day of that week. (The ISO WeekDate Calendar uses a week (and therefore a year) that begins on a Monday, probably so that the weekend won't be split in half.) The ISO WeekDate Calendar is, as I said, widely used internationally, by Companies & Governments, for their planning of business & governmental dates & events. ...making it easy to plan them in advance once, and then leave them, because it's a fixed calendar. Of course the resulting dates then have to be eventually translated into Roman-Gregorian dates. ...but they wouldn't have to, if we adopted the ISO WeekDate calendar as our civil calendar, worldwide. ISO WeekDate has the great advantage of use-precedent. ...lots of it. I personally like the ISO WeekDate as the best calendar-reform proposal. But, recognizing that many people wouldn't want to give up the months, and would want to keep them for familiarity & continuity, the 30,30,31 month-system could be a good alternative proposal, if ISO WeekDate isn't accepted. But it has been argued that ISO WeekDate is so convenient, and already so widely-used, that it could easily edge-out the Roman-Gregorian Calendar, from the bottom up, by increasingly wide use, if companies & government start using it so much that the public start finding it convenient to use it too. So those are my two disagreements with Gorman's proposal, and my alternative suggestions. But I should comment on the leapyear rule. Actually, the ISO WeekDate Calendar deals with that in a really easy, natural, simple & obvious way. Each ISO WeekDate year starts on whatever Monday is closest to the Gregorian January 1st of that year. So, for example, this year, 2017, the Gregorian year started on a Sunday. So the nearest Monday to Gregorian January 1st was January 2nd. That Monday, Gregorian January 2nd, is the day on which ISO WeekDate 2017 started. As I said, today, in the ISO WeekDate Calendar, is: 4 Saturday (or 2017W046) That way of defining the start of the ISO WeekDate year (the Monday closes to Gregorian January 1st) is called the Nearest-Monday year-start system. Note that the Nearest-Monday year-start system doen't have to mention leapyears or leapweeks at all. It's *effectively* a leapweek calendar, because some of the years have 53 weeks instead of 52. But the simple Nearest-Monday year-start rule doesn't need to mention leapyears or leapweeks. Not only is it used with the ISO WeekDate Calendar, but of course it could also be used with a 30,30,31 quarters calendar too. Calendar reform advocates propose all manner of different leapyear systems. But there's nothing wrong with the Nearest-Monday year-start system, and conversations have suggested to me that Nearest-Monday would be the favorite way to make a fixed calendar. In fact, with Nearest-Monday, the maximum displacement of dates with respect to seasons, is barely more than the ideal minimum that could be achieved by the fanciest leapyear system. I also propose a fancier, deluxely-adjustable system, but I won't try your patience with that here, because Nearest-Monday is entirely good enough, and is the system with obviously by far the best acceptance-potential. Michael Ossipoff. On Sat, Jan 28, 2017 at 3:38 PM, Dan-George Uza wrote: > A bit off topic, but I enjoyed this quite a lot! > > https://youtu.be/EcMTHr3TqA0 > > Dan > > --- > https://lists.uni-koeln.de/mailman/listinfo/sundial > > > --- https://lists.uni-koeln.de/mailman/listinfo/sundial
Re: Why we should reform the Calendar
enough to cause any significant calendar-displacement with respect to the seasons.. To quote one calendarist: "Welcome to the 1st millennium of the Age of the June Solstice Year!" So the current period of remarkable stability of the length of the June Solstice year has only been in effect since roughly the time of the Battle of Hastings. So of course the June Solstice tropical year has great appeal as the mean-year for a leapyear-rule. And that wouldn't be unfair to the South, because the Winter Solstice is celebrated as much as the Summer Solstice. Though my calendar-proposal is to use the mean tropical year, or the arithmetic average of the March & September Equinox years as the mean year for a leapyear-rule, I'd have no objection at all to the use of the June Solstice year, which has great appeal. The point is that we can choose what tropical year we use for a mean year for a calendar's leapyear-rule. But if we use the Nearest-Monday year-start rule, we're inheriting the Gregorian's use of the March Equinox year as the tropical year that the calendar's mean year approximates. That isn't really a problem, but it would be nice to make that choice for ourselves--as my Minimum-Displacement leapyear-rule (defined later) does. The other things is that the Gregorian's 365.2425 day mean-year, being more approximate, results in more drift (with respect to its intended tropical year length) than would a more precise approximation. And when the calendar's relation between date & ecliptic longitude oscillates, in the leapyear-system, about what central date/season relation does it oscillate? Wilth the Gregorian, and hence with Nearest-Monday, that's out of our hands, decided for us. I'm not saying that that's a problem either. It's just that it would be *nice* to have the luxury of choosing, for ourselves, 1) what tropical year we want the calendar's mean-year to approximate; and 2) what date/season relation we want for the calendar's center of oscillation. The Minimum-Displacement leapyear-rule allows the luxury of making our own choice of those two adjustment-parameters. This posting is already very long, and so I'll save the Minimum-Displacement leapyear-rule for a (immediately subsequent) next posting. Michael Ossipoff I seems to me that the March Equinox tropical year is something like 365.24239 On Sat, Jan 28, 2017 at 8:54 PM, Michael Ossipoff wrote: > I don't think it's really off-topic, because, with sundials, we're > interested in the EqT, which is given in terms of the calendar's dates. > > Though Gorman is a comedian, he's obviously given the matter some serious > consideration, and I perceive some serious interest in calendar-reform. > > But I have a few disagreements with his proposal: > > > > *1. Blank Days:* > Gorman proposes a "fixed calendar", a calendar that will be the same for > every year. I have no objection to that. After all, so far as we know > (except for each year setting a new record for increasing global warming) > what we can expect from each year, nature-wise, is really the same. So, why > should two successive years have different calendars, with different dates > having different days-of-the-week? > > So far so good. There are two ways proposed for achieving a fixed > calendar: > > *1. Blank Days:* > > A fixed calendar must have a number of days that's a multiple of 7, That's > what enables each calendar to start on the same day of the week, allowing > every date to have a day-of-the-week that doesn't change from year to year. > So Gorman would make one of the 365 days a "blank day", a day that isn't a > day of the week. Then the days-of-thes-week would resume after that day. so > the year would have only 364 days that are days of the week. That being a > multiple of 7, each year will start on the same day of the week, as desired. > > Problem: I'm sorry, but it doesn't make any sense for the day after a > Saturday to be anything other than a Sunday. ...or for there to be an > intervening day between a Saturday & a Sunday. > > Speaking for myself, I completely reject "blank-days". And I'm not the > only one. Elizabeth Achellis, over several decades, up to around 1955, > proposed a fixed calendar with blank-days. The League of Nations, and later > the U.N. were giving serious consideration to it, and it might have been > accepted, except for the strong opposition to the blank-days, > > A compromise was offered to Achellis: A leap-week (described in the next > section below), to achieve a fixed calendar. She wouldn't accept that > compromise, and her proposal was indefinitely tabled around 1955, and never > got anywhere since. Yo
Re: Why we should reform the Calendar
On Sun, Jan 29, 2017 at 2:41 PM, Robert Kellogg wrote: > Michael goes off looking for the ideal tropical year There isn't an "ideal tropical year", but, as a choice for a leapyear-rule's mean-year, the length of the mean tropical year (MTY) is best for year-round reduction of longterm calendar-drift. ...and the average of the lengths of the March & September Equinox tropical years (I'll call that the Average Equinox Year (AEY) ) is a compromise between the vernal equinoxes of the North & the South. > , perhaps ignoring effects of the earth's nutations. > Of course. The nutations are small in amplitude & period. They aren't part of calendar rules. The mean equinox (nutations averaged-out) is the one that is meant when the equinox is spoken of with regard to calendars. > I'll still take the one of 1900, most importantly because it defines the > SI second. The SI second was defined as 1/86,400 of a mean solar day, for some year in the early 19th century. I don't remember exactly what year that was. 1820? 1840? 1850? Evidently it isn't practical to update the length of the SI second, but that doesn't mean that calendars have to be based on the ephemeris day, or atomic day, consisting of 86,400 SI seconds, when that's known to be different from today's mean solar day. That's why I suggest 365.24217 instead of 365.24219 for the length of the mean tropical year (MTYI. It makes sense to base a calendar leap-year rule's mean-year on the actual length of a tropical-year (whichever one we want to use) on the length of that tropical year in* today's* mean days. > > > So, contemplating changing the year is non trivial. Evidently there must be some reason why it would be impractical to update the length of the SI second. But it isn't necessary to call a MTY 365.24219 days, when it's really 365.24217 mean days long. ...for the purposes of a calendar leapyear rule. There's inevitable inaccuracy due to rounding-off, and due to gradual change in the lengths of all the tropical years, including the MTY. But that doesn't mean we have to intentionally add avoidable error. > Contemplating decoupling UTC from the rotation of the earth (ie necessity > of being within .9 sec of UT1) likewise has significant consequences. > Let's let the IAU chart the future of time. Sure, but it isn't necessary to base a calendar on a day that isn't today's mean solar day. Michael Ossipoff > Dennis and Ken, if you're listening to this discussion, please chime in. > > > On 1/29/2017 12:27 PM, sundial-requ...@uni-koeln.de wrote: > >> Send sundial mailing list submissions to >> sundial@uni-koeln.de >> >> To subscribe or unsubscribe via the World Wide Web, visit >> https://lists.uni-koeln.de/mailman/listinfo/sundial >> or, via email, send a message with subject or body 'help' to >> sundial-requ...@uni-koeln.de >> >> You can reach the person managing the list at >> sundial-ow...@uni-koeln.de >> >> When replying, please edit your Subject line so it is more specific >> than "Re: Contents of sundial digest..." >> >> >> Today's Topics: >> >> 1. Re: Why we should reform the Calendar (Michael Ossipoff) >> >> >> -- >> >> Message: 1 >> Date: Sun, 29 Jan 2017 12:27:56 -0500 >> From: Michael Ossipoff >> To: Dan-George Uza >> Cc: sundial list >> Subject: Re: Why we should reform the Calendar >> Message-ID: >> > gmail.com> >> Content-Type: text/plain; charset="utf-8" >> >> >> Here are two (unimportant) objections to the Nearest-Monday year-start >> system: >> >> 1. It's based on the Gregorian leapyear-rule, meaning that it isn't >> self-contained & free-standing. Mostly an aesthetic objection, and I don't >> consider it important. >> >> 2. It inherits certain properties of the Gregorian Calendar, which could >> otherwise be adjustable, choose-able. This, too, I consider only an >> aesthetic objection. >> >> Here are the properties that I refer to: >> >> The Gregorian leapyear-rule was designed to minimize the date's variation >> at the (northern) Vernal Equinox, the March equinox. >> >> We often hear it said that the mean tropical year is the time from one >> March equinox to the next. Not so. That's because the length of a tropical >> year depends on at what point of the ecliptic it's measured. >> >> A tropical year is a seasonal year, the
Re: Why we should reform the Calendar
*The Minimum-Displacement Leapyear Rule:* This is a leap-week leapyear-rule. The common (non-leap) year is 364 days long. A leapyear is 364 + 7 = 371 days long. The leapweek is added at the end of the year, becoming part of that year Epoch: Gregorian January 2, 2017 is this calendar's start, being this calendar's January 1, 2017.. *Variable: * D D stands for "displacement". Though this definition isn't needed for the specification of this leapyear-rule, displacement is a change or difference in the relation between date and ecliptic longitude. Actually the progress of a mean-year, or an approximation to one, usually stands in for ecliptic longitude in a leapyear-rule. D, here, is the difference between the current year's displacement from the year's desired relation between date & ecliptic longitude (where ecliptic longitude is represented by the progress of the mean-year). *Constants:* 1. Dzero is the starting value of D, the value of D at the calendar's epoch. (The epoch is the time at which the calendar is defined to start). 2. Y is the length of the leapyear-rule's mean-year (I sometimes call it the "reference-year" too). For the value of Dzero, I offer -.6288 or 0. Of those two, I recommend -.6288 (...for reasons I'll get to later in this post.) A Dzero of -.6288 means that the year is, at its epoch, displaced by -.6288 days from its desired relation of date & season. For the value of Y, I recommend 365.24217, the approximate number of mean solar days in a mean tropical year (MTY). Dzero & Y are the two adjustment-parameters that I spoke of in a previous post. *Year-End Change in D:* At the end of a calendar year (whether common or leap), the value of D changes by an amount equal to Y minus the length of that year in days. If that change would otherwise result in a D value greater than +3.5, then 7 days are added to the end of that year, before implementing the paragraph before this one. ...making that year a leapyear. [end of Minimum-Displacement leapyear-rule] In this way, the value of D is kept within the limits of -3.5 days to + 3.5 days. D is a good measure of the calendar's displacement from its desired date/season relation defined by Dzero. The -.6288 value of Dzero is consistent with a desired relation of calendar-date and ecliptic-longitude (...where ecliptic-longitude is represented by the progress of the 365.24217 day mean-year) that is the midpoint of the extremes of the values that that relation had between January 1, 1950 and January 1, 2017. ...in order that the calendar's center of displacement-oscillation be the average of its variation-extremes since January 1, 1950. ...so that the calendar's date-season relation will stay close to where it has been during the experience of currently-living humans. Though I like the ISO WeekDate calendar, and it's said that it has a good chance of eventually displacing Roman-Gregorian, via gradually-increasing usage, my proposal is a calendar using the 30,30,31 quarters, and the Minimum-Displacement leapyear-rule, with Dzero = -.6288, and with Y = 365.24217. I should add that calculation, with the Minimum-Displacement rule, of durations, day-of-the-week, & displacements are no more difficult than the same calculations with the Gregorian leapyear-rule. And determination of whether a particular far-distant year is a leapyear is no more difficult than those calculations. ...and of course the determination of whether the *next* year is a leapyear is just a matter of directly applying the leapyear-rule, as defined above. . ..and of course, any time when the current year is a leapyear, that fact will be amply announced long before the end of that year. Michael Ossipoff approx. 26N, 80W --- https://lists.uni-koeln.de/mailman/listinfo/sundial
Re: Genuine or not?
It doesn't seem genuine to me. It isn't just that there doesn't seem to be a way of moving the upper end of the string to the other latitude-marks. It's also that you can't just change the angle of the gnomon, for a different latitude, and use the same hour-lines. So there seems to be no purpose for the latitude-marks on the inside of the vertical, piece--other than to make it look adjustable for latitude. Michael Ossipoff On Mon, Feb 20, 2017 at 9:57 AM, Dan-George Uza wrote: > Hello! > > There's a diptych sundial on sale for about 80 euros supposedly dating > from 1920. > > Do you think this is genuine? I think it is a modern replica. > > http://anticariatulnou.ro/diverse/antichitati-artizanat- > colectionabile/cadran-solar-cu-busola-antica-din-lemn-diptic.html > > The string does not seem to be adjustable for latitude, I see only one > hole (it's fixed at 42 deg.). Why then go through the trouble of printing > the latitudes for European cities on the back? > > One thing I find interesting is the plumb bob and the orifice on the > vertical plate. I think it is meant to align the piece to the vertical. I > haven't seen this before. > > Thanks, > > Dan Uza > Romania > > --- > https://lists.uni-koeln.de/mailman/listinfo/sundial > > > --- https://lists.uni-koeln.de/mailman/listinfo/sundial
Re: Dial face colouration
tdoor sundial :^) There are a lot of questions that I'd ask about that. I'll save those for another post, sometime. Well, one question now: Were pillar-dials, the ones at street-intersections or town-squares, always aligned with the cardinal directions? Doing so would mean that the shadow-casting edge, for the east and west faces, would be parallel to the dial-face, reducing the hour-coverage for those faces. So did they sometimes make it a declining dial, so that the shadow-casting edge would intersect the dial surface, on all four faces? I've considered eventually, when I get around to it, making a pillar-dial mounted on a lamp-post. It would be in the form of a hinged wooden box, a cube-dial without the top and bottom faces, with holes in the top & bottom, and hinged to close onto the lamp-post. The inside edge of the holes in the top & bottom would be rubber-lined, for squeezing onto the lamp-post without damaging it, when closing the box onto the lamp-post. There would be a bolt-and-wingnut on the corner-edge opposite the hinge, to tighten the hinged box onto the lamp-post. I'd consider declining-dials on the four faces, to that the shadow-casting edge would intersect the dial-face, on all four faces. Were pillar-dials usually, often, or ever made that way? Michael Ossipoff > > --- https://lists.uni-koeln.de/mailman/listinfo/sundial
Re: Dial face colouration
It seems to me that Steve's question has been mostly disregarded rather than answered. Not having experience with translucent dial-faces, I didn't know about their lack of accuracy, and I certainly can't disagree with what two people have said about that. It means that the advantage of a translucent dial, for omnidirectional reading, comes with a disadvantage of less precise accuracy. But of course a high-mounted dial intended for relatively distant reading might not be as concerned with fine accuracy as with omnidirectional viewing. And so translucent dials for all-directions viewing certainly aren't ruled-out. Steve's main question was about the choice of dial-face hue, saturation and brilliance, for easy and safe dial-reading. It seems to me that Steve's question has been mostly disregarded and discounted rather than answered. I lied. I said that I can't speak from experience on that matter. But my experience with a few paper-on-cardboard tablet-dials is sufficient to say this: >From my experience, I can say that you definitely don't want a white dial-face. As I said, my first dial had a white dial-face. After that, I switched to brown, which was a big improvement in usability. I suggest brown instead of white. Someone implied that, the more contrast (between light and shadow), the better. Not so, when the dial-face is too white to look at in bright sunlight. As for gray: Gray reflects the visible wavelengths in a relatively equal mix, resulting in no perceived hue. If some hues are (at least relatively) to be avoided, then obviously gray isn't what you want. At each end of the visible spectrum, there is, of course, radiation that isn't visible. Infrared (IR) and ultraviolet (UV). One possible disadvantage of that is that, when you don't perceive it or its intensity, then of course you could conceivably get a dangerous amount (accutely or cumulatively) without any perception of it. For example, never look at the sun when, due to a haze, or due to the sun being low in the sky, the sun doesn't look bright. You don't have any perception of how ingtense the UV or IR is. It could burn your eye without any feeling of discomfort. (I don't know which of those is more dangerous, but there have been official warnings to never look at the sun when it seems less bright due to haze or low altitude.) Aside from that, there's been evidence that, when people spend a lot of time outdoors, in bright sunny climate, then many years of exposure to the bright blue light can cause some long-term cumulative damage. So maybe blue isn't the most desirable hue. Yellow, beings the complement of blue, looks yellow because it absorbs blue, removes blue from the light that it reflects. Also, yellow isn't particularly close to either end of the visible spectrum. Brown is defined as: "Any of a group of colors between red and yellow in hue, of medium to low brilliance, and of moderate to low saturation." Then, dark brown would be brown with particularly low brilliance--a desirable attribute for a sundial-face. Might that be the best color for a dial-face? Tan is defined as: "Light yellowish brown." ...suggesting more brilliance than brown (but surely a lot less than white), and enough saturation to be perceived as yellow, which seems a good thing. Brown, especially dark brown, or maybe tan, sound like acceptable colors for a dial-face. By the way, beige is defined as: "A variable color averaging light grayish yellowish brown." Sounds like tan, but with distinct grayness, lower saturation, making it probably less desirable. In my previous post I said that I bought brown construction-paper, but didn't use it, and, instead, just marked the hour-lines on the corrugated cardboard instead of using paper. Actually, I probably did use the brown construction-paper. It looks better of course, and it allowed me to conveniently use a carbon-paper template that I'd prepared for drawing the hour-lines. Maybe the plain cardboard dial-face would have easier construction in one way, and less easy construction in another way. Maybe I tried one all-cardboard dial. It was a long time ago. Michael Ossipoff On Fri, Feb 24, 2017 at 1:04 PM, Steve Lelievre < steve.lelievre.can...@gmail.com> wrote: > Fellow sundiallers, > > I’m planning to make my next sundial from outdoor grade UV resistant > plastic sheeting. These come in a range of colours and I want to choose one > that works well for a sundial. Assuming I get the material grit-blasted or > somehow treated so that it not shiny, and leaving aesthetic considerations > aside, what light-related attributes should I be looking for? > > As anyone who has played with paper sundials knows, a white surface is > hard to look at in full sun, even if non-shiny; black would not show any > shadow. I nee
Re: Dial face colouration
Well it's 1) How bright the dial face has to be for it to show a shadow when the sun is as low as it can be at the sundial's mounting-location. 2) How un-bright does the dial need to be at noon on the summer solstice, so that it won't be too bright to look at. *As for #1* , you can find that out whenever the sun is as low as the lowest it can get at the sundial's mounting-location. And, if it isn't visible that low at this time of year, due to obstacles like a tree or a house, then of course you can go to a different location without that obstruction. So you can easily find the answer to #1 now. So, at a location where the sun is visible as low in the sky as it can ever get at the mounting-location, try brown, and, if the shadow isn't visible, try light-brown, and then (dark, ordinary, and light) tan, and then yellow. I rather doubt that it will require something as bright as yellow, unless the dial will receive sunlight all the way to sunset. Most likely some brown or tan will be light enough, depending on how low the sun can be and still shine on the dial (which depends on the trees, buildings and other obstructions in your yard. *As for #2: * One thing that you already know is that matte-black shows a shadow when the sun is at its brightest, because it showed a shadow even during your recent winter experiment. So matte-black will show a shadow at the solstice-noon too. Whatever shade of brown/tan/yellow is barely light enough to show a shadow when the sun is at its lowest for your dial-location, that's a first thing to try at summer-solstice noon. But, if that's too bright at summer solstice noon, then you want to find out how bright it's permissible for the dial to be, at summer solstice noon, without being too bright. For that, to be really sure, I agree that you have to wait for the summer solstice. But you can get a good estimate now, if you have a formula for sunlight intensity as a function of solar altitude: Find out, from the formula, and from he noon solar altitudes now and at the solstice, how many time more intense the sunlight is at summer-solstice noon, as compared with noon on some day this week. Find the sine of the sun's altitude at noon on some day this week. That's also the cosine of the sun's distance from the dial-normal (perpendicular line) at noon. Multiply that cosine by the factor by which the sun will be brighter at solstice-noon, as compared to that noon this week. Find the angle whose cosine equals the result of that multiplication. Find the difference between that angle and the sun's angle from the zenith on this week's observing-day. Tip your color-sample southward up from the horizontal, at noon, on this week's observing-day, to get the sunshine-intensity that a horizontal surface would receive on at summer-solstice noon. So, with the color-sample tipped up southward at that angle, find the shade that won't be too bright at solar noon on this week's observing day. Hopefully there's a shade that is bright enough when the sun is at its visible lowest at the dial-location, and still isn't too bright at solstice noon (on a horizontal dial). I'd bet that some brown or tan would be likely to meet both requirements. Michael Ossipoff On Tue, Feb 28, 2017 at 5:09 PM, Steve Lelievre < steve.lelievre.can...@gmail.com> wrote: > John, thanks for the clarification, and your patience with my questions. > > All, I'm off to buy some photographic mattes to do experiements with. This > is all about having a horizontal dial face that is not too bright to view > even in the summer midday sun - so I'll go quiet now and report back after > the summer solstice. > > Steve > > > > On 2017-02-28 1:40 AM, John Lynes wrote: > > Hi Steve, > I'm sorry I've confused you. > > ... > > The take-home conclusion is that there is no single ideal reflectance for > the plate of a sundial. It varies with the sky illuminance. When Weber's > Law prevails, a reflectance of about 60 per cent is likely to be a safe bet. > > > > --- > https://lists.uni-koeln.de/mailman/listinfo/sundial > > > --- https://lists.uni-koeln.de/mailman/listinfo/sundial
Re: Dial face colouration
What am I saying?? You don't need the formula for the sun's brightness at different altitudes. You just need to tip the color-sample card, from the horizontal, toward the sun by an amount that's equal to the amount by which the summer-solstice deciination (23.44 degrees?) will be greater than the solar declination on the day of the experiment this week. That will give the color-sample card the same solar illumination that it will have at solstice noon. On Tue, Feb 28, 2017 at 5:09 PM, Steve Lelievre < steve.lelievre.can...@gmail.com> wrote: > John, thanks for the clarification, and your patience with my questions. > > All, I'm off to buy some photographic mattes to do experiements with. This > is all about having a horizontal dial face that is not too bright to view > even in the summer midday sun - so I'll go quiet now and report back after > the summer solstice. > > Steve > > > > On 2017-02-28 1:40 AM, John Lynes wrote: > > Hi Steve, > I'm sorry I've confused you. > > ... > > The take-home conclusion is that there is no single ideal reflectance for > the plate of a sundial. It varies with the sky illuminance. When Weber's > Law prevails, a reflectance of about 60 per cent is likely to be a safe bet. > > > > --- > https://lists.uni-koeln.de/mailman/listinfo/sundial > > > --- https://lists.uni-koeln.de/mailman/listinfo/sundial
Re: Dial face colouration
Alright, it isn't that simple, and I was closer to right the first time. Find out by what factor (f) the sun will be brighter, due to higher altitude, on the solstice, compared to the day of your experiment this week. Calculate the sun's zenith angle at summer solstice noon, and find the cosine of that zenith angle. Multiply that cosine by f, and find the angle (A) with a cosine equal to that product. Tip the color-sample card so that its normal is that many degrees away from the sun. Do that by subtracting the absolute value of the sun's declination on the experiment day this week, from the complement of your latitude, to find the sun's altitude on the noon of the experiment. Add or subtract A from that altitude. Tip the color-sample card so that its north end is tipped up by the complement of that angle. In that way, the sunlight intensity on the color-sample card is what it will be on the horizontal dial at summer solstice noon. (unless I've made another error) Michael Ossipoff On Wed, Mar 1, 2017 at 10:27 PM, Michael Ossipoff wrote: > What am I saying?? > > You don't need the formula for the sun's brightness at different altitudes. > > You just need to tip the color-sample card, from the horizontal, toward > the sun by an amount that's equal to the amount by which the > summer-solstice deciination (23.44 degrees?) will be greater than the solar > declination on the day of the experiment this week. > > That will give the color-sample card the same solar illumination that it > will have at solstice noon. > > On Tue, Feb 28, 2017 at 5:09 PM, Steve Lelievre < > steve.lelievre.can...@gmail.com> wrote: > >> John, thanks for the clarification, and your patience with my questions. >> >> All, I'm off to buy some photographic mattes to do experiements with. >> This is all about having a horizontal dial face that is not too bright to >> view even in the summer midday sun - so I'll go quiet now and report back >> after the summer solstice. >> >> Steve >> >> >> >> On 2017-02-28 1:40 AM, John Lynes wrote: >> >> Hi Steve, >> I'm sorry I've confused you. >> >> ... >> >> The take-home conclusion is that there is no single ideal reflectance for >> the plate of a sundial. It varies with the sky illuminance. When Weber's >> Law prevails, a reflectance of about 60 per cent is likely to be a safe bet. >> >> >> >> --- >> https://lists.uni-koeln.de/mailman/listinfo/sundial >> >> >> > --- https://lists.uni-koeln.de/mailman/listinfo/sundial
Construction-Principle of Capuchin & Universal Capuchin Dials???
I'm not asking about the *instructions *for constructing Capuchin and Universal Capuchin dials. I'm asking about the principle, the explanation, the justification, for their construction. Some websites have said or implied that it has to do with an orthographic planisphere. I'm familiar with the use of a universal planisphere, an azimuthal projection of the celestial sphere in equatorial-aspect. ...but it isn't entirely clear how that relates to the Capuchin dials. I found a handwaving explanation on the web. I've pasted its diagram, and some of its "explanation", below in this e-mail. The explanation says that the diagram below, an orthographic projection of the celestial-sphere, looks just like a Capuchin dial. And that's supposed to be an explanation. So, how does an orthographic projection of the celestial-sphere lead to a justification and explanation of the construction of a Capuchin or Universal Capuchin dial? Can anyone here explain that? If so, the explanation would be appreciated. Michael Ossipoff [image: Inline image 1] --- https://lists.uni-koeln.de/mailman/listinfo/sundial
Re:
Thank you--Yes that's the article that I quoted, and from which I got the diagram that I posted here. That's the article that doesn't really explain anything. It shows a picture of a Capuchin dial (figure 1), and also a diagram of an orthographic projection of the celestial sphere (figure 2). Its explanation basically consists of saying that figure 2 looks like figure 1. But, for one thing, of course it doesn't. For one thing, 1. In figure 2, the parallel lines are parallel to the horizon. In figure 1, the parallel lines in the bottom half-circle are perpendicular to the direction of the sun. 2. In figure 2, the small circle to the left is centered within the sun's extreme diurnal positive and negative altitudes, at the depicted solar declination. ...but, in figure 1, it's the circle with the parallel lines is just centered at the middle of the page. 3. In figure 2, the sun is shown at a southern declination, something that is seemingly in disagreement with figure 1. But all that is aside from the fact that the article just doesn't give an explanation, other than its handwaving reference to the alleged similarity of figure 1 and figure 2. Anyway, yes, that's the article to which I was referring. So my question is, "What would be a genuine explanation and justification for the construction of the Capuchin and Universal Capuchin dials? Michael Ossipoff 2017-05-09 15:49 GMT-04:00 Putowsky via sundial : > Diese Nachricht wurde eingewickelt um DMARC-kompatibel zu sein. Die > eigentliche Nachricht steht dadurch in einem Anhang. > > This message was wrapped to be DMARC compliant. The actual message > text is therefore in an attachment. > > -- Forwarded message -- > From: Putowsky > To: Michael Ossipoff > Cc: sundial list > Bcc: > Date: Tue, 9 May 2017 21:49:58 +0200 > Subject: Re: Construction-Principle of Capuchin & Universal Capuchin > Dials??? > Here is the complete article. > > http://articles.adsabs.harvard.edu//full/1961JRASC.. > 55...49S/054.000.html > > putow...@yahoo.com > > On May 9, 2017, at 8:50 PM, Michael Ossipoff > wrote: > > I'm not asking about the *instructions *for constructing Capuchin and > Universal Capuchin dials. I'm asking about the principle, the explanation, > the justification, for their construction. > > Some websites have said or implied that it has to do with an orthographic > planisphere. I'm familiar with the use of a universal planisphere, an > azimuthal projection of the celestial sphere in equatorial-aspect. ...but > it isn't entirely clear how that relates to the Capuchin dials. > > I found a handwaving explanation on the web. I've pasted its diagram, and > some of its "explanation", below in this e-mail. > > The explanation says that the diagram below, an orthographic projection of > the celestial-sphere, looks just like a Capuchin dial. And that's supposed > to be an explanation. > > So, how does an orthographic projection of the celestial-sphere lead to a > justification and explanation of the construction of a Capuchin or > Universal Capuchin dial? > > Can anyone here explain that? If so, the explanation would be appreciated. > > Michael Ossipoff > > > > --- > https://lists.uni-koeln.de/mailman/listinfo/sundial > > > --- > https://lists.uni-koeln.de/mailman/listinfo/sundial > > > --- https://lists.uni-koeln.de/mailman/listinfo/sundial
Re:
Sure, analytic geometry verifies that the Universal Capuchin dial agrees with the formula that relates time, altitude, declination and latitude. But that isn't how medieval astronomers &/or dialists arrived at the construction of the Capuchin dials. Michael Ossipoff On Tue, May 9, 2017 at 4:13 PM, Michael Ossipoff wrote: > Thank you--Yes that's the article that I quoted, and from which I got the > diagram that I posted here. > > That's the article that doesn't really explain anything. > > It shows a picture of a Capuchin dial (figure 1), and also a diagram of an > orthographic projection of the celestial sphere (figure 2). Its explanation > basically consists of saying that figure 2 looks like figure 1. > > But, for one thing, of course it doesn't. > > For one thing, > > 1. In figure 2, the parallel lines are parallel to the horizon. In figure > 1, the parallel lines in the bottom half-circle are perpendicular to the > direction of the sun. > > 2. In figure 2, the small circle to the left is centered within the sun's > extreme diurnal positive and negative altitudes, at the depicted solar > declination. > > ...but, in figure 1, it's the circle with the parallel lines is just > centered at the middle of the page. > > 3. In figure 2, the sun is shown at a southern declination, something that > is seemingly in disagreement with figure 1. > > But all that is aside from the fact that the article just doesn't give an > explanation, other than its handwaving reference to the alleged similarity > of figure 1 and figure 2. > > Anyway, yes, that's the article to which I was referring. So my question > is, "What would be a genuine explanation and justification for the > construction of the Capuchin and Universal Capuchin dials? > > Michael Ossipoff > > > 2017-05-09 15:49 GMT-04:00 Putowsky via sundial : > >> Diese Nachricht wurde eingewickelt um DMARC-kompatibel zu sein. Die >> eigentliche Nachricht steht dadurch in einem Anhang. >> >> This message was wrapped to be DMARC compliant. The actual message >> text is therefore in an attachment. >> >> -- Forwarded message -- >> From: Putowsky >> To: Michael Ossipoff >> Cc: sundial list >> Bcc: >> Date: Tue, 9 May 2017 21:49:58 +0200 >> Subject: Re: Construction-Principle of Capuchin & Universal Capuchin >> Dials??? >> Here is the complete article. >> >> http://articles.adsabs.harvard.edu//full/1961JRASC..55... >> 49S/054.000.html >> >> putow...@yahoo.com >> >> On May 9, 2017, at 8:50 PM, Michael Ossipoff >> wrote: >> >> I'm not asking about the *instructions *for constructing Capuchin and >> Universal Capuchin dials. I'm asking about the principle, the explanation, >> the justification, for their construction. >> >> Some websites have said or implied that it has to do with an orthographic >> planisphere. I'm familiar with the use of a universal planisphere, an >> azimuthal projection of the celestial sphere in equatorial-aspect. ...but >> it isn't entirely clear how that relates to the Capuchin dials. >> >> I found a handwaving explanation on the web. I've pasted its diagram, and >> some of its "explanation", below in this e-mail. >> >> The explanation says that the diagram below, an orthographic projection >> of the celestial-sphere, looks just like a Capuchin dial. And that's >> supposed to be an explanation. >> >> So, how does an orthographic projection of the celestial-sphere lead to a >> justification and explanation of the construction of a Capuchin or >> Universal Capuchin dial? >> >> Can anyone here explain that? If so, the explanation would be appreciated. >> >> Michael Ossipoff >> >> >> >> --- >> https://lists.uni-koeln.de/mailman/listinfo/sundial >> >> >> --- >> https://lists.uni-koeln.de/mailman/listinfo/sundial >> >> >> > --- https://lists.uni-koeln.de/mailman/listinfo/sundial
Re: Construction-Principle of Capuchin & Universal Capuchin Dials
Yvon-- Thanks for providing that information and links. If the links' explanation seemed satisfactory to one dialist, then I expect that it *is* satisfactory--and a satisfactory explanation is what I'm looking for. I'll check out those two links. Yes, it isn't an easy question, but even a difficult explanation can give me a good hint, regarding the nature of where the construction came from. So thanks again for the help, the information, the links! Michael Ossipoff On Wed, May 10, 2017 at 4:56 PM, Yvon Massé wrote: > Michael, > > Some years ago, I spent a lot of time to search a simple geometrical > justification of these kind of dial. The best way I found is: > - for the Capuchin: from the orthographic projection of the celestial > sphere on the local meridian (fig. 1) > - for the Universal Capuchin: from the orthographic projection on the hour > plane of the Sun (fig. 4) > > These figures are detailed here: > http://cadrans-solaires.scg.ulaval.ca/v08-08-04/pdf/XIII-4-p10-4.pdf > > and the links between the figures and the dial are briefly explained here: > http://gnomonique.fr/divers/anal_3_angc.pdf > > Of course, it isn't quite simple but, perhaps, you will find some interest > in these articles. > > Best regards > > Yvon > > > Le 09/05/2017 20:50, sundial-requ...@uni-koeln.de a écrit : > >> >> I'm not asking about the *instructions *for constructing Capuchin and >> Universal Capuchin dials. I'm asking about the principle, the explanation, >> the justification, for their construction. >> >> Some websites have said or implied that it has to do with an orthographic >> planisphere. I'm familiar with the use of a universal planisphere, an >> azimuthal projection of the celestial sphere in equatorial-aspect. ...but >> it isn't entirely clear how that relates to the Capuchin dials. >> >> I found a handwaving explanation on the web. I've pasted its diagram, and >> some of its "explanation", below in this e-mail. >> >> The explanation says that the diagram below, an orthographic projection of >> the celestial-sphere, looks just like a Capuchin dial. And that's >> supposed >> to be an explanation. >> >> So, how does an orthographic projection of the celestial-sphere lead to a >> justification and explanation of the construction of a Capuchin or >> Universal Capuchin dial? >> >> Can anyone here explain that? If so, the explanation would be appreciated. >> >> Michael Ossipoff >> >> --- > https://lists.uni-koeln.de/mailman/listinfo/sundial > > --- https://lists.uni-koeln.de/mailman/listinfo/sundial
Re: Capuchin Dials
Hi Peter-- Thanks for the reply and info. Yes, I hope that Fred Sawyer will post about the derivation of the construction of the Capuchin and Universal Capuchin dials. Fred, would you paste some of your lecture material, about that, into a list e-mail here? Michael Ossipoff On Wed, May 10, 2017 at 10:33 PM, Peter Mayer wrote: > Hi Michael, > > I've been hoping that Fred Sawyer would respond to your enquiry. At > last year's NASS Conference, Fred gave a talk on Rectilinear Altitude > Dials. It was, as always, a tour de force...and way over my head! But in > it Fred demonstrated the unity of Capuchin, Regiomantanus, Peter Apian, > etc. etc. plus his own earlier Nomographic Dial...as well as novel dials > based on the same principles. > > best wishes, > > Peter > > On 11/05/2017 01:46, Michael Ossipoff wrote: > > > Sure, analytic geometry verifies that the Universal Capuchin dial agrees > with the formula that relates time, altitude, declination and latitude. > > But that isn't how medieval astronomers &/or dialists arrived at the > construction of the Capuchin dials. > > Michael Ossipoff > > On Tue, May 9, 2017 at 4:13 PM, Michael Ossipoff > wrote: > >> Thank you--Yes that's the article that I quoted, and from which I got the >> diagram that I posted here. >> >> That's the article that doesn't really explain anything. >> >> It shows a picture of a Capuchin dial (figure 1), and also a diagram of >> an orthographic projection of the celestial sphere (figure 2). Its >> explanation basically consists of saying that figure 2 looks like figure 1. >> >> But, for one thing, of course it doesn't. >> >> For one thing, >> >> 1. In figure 2, the parallel lines are parallel to the horizon. In figure >> 1, the parallel lines in the bottom half-circle are perpendicular to the >> direction of the sun. >> >> 2. In figure 2, the small circle to the left is centered within the sun's >> extreme diurnal positive and negative altitudes, at the depicted solar >> declination. >> >> ...but, in figure 1, it's the circle with the parallel lines is just >> centered at the middle of the page. >> >> 3. In figure 2, the sun is shown at a southern declination, something >> that is seemingly in disagreement with figure 1. >> >> But all that is aside from the fact that the article just doesn't give an >> explanation, other than its handwaving reference to the alleged similarity >> of figure 1 and figure 2. >> >> Anyway, yes, that's the article to which I was referring. So my question >> is, "What would be a genuine explanation and justification for the >> construction of the Capuchin and Universal Capuchin dials? >> >> Michael Ossipoff >> >> >> 2017-05-09 15:49 GMT-04:00 Putowsky via sundial : >> >>> Diese Nachricht wurde eingewickelt um DMARC-kompatibel zu sein. Die >>> eigentliche Nachricht steht dadurch in einem Anhang. >>> >>> This message was wrapped to be DMARC compliant. The actual message >>> text is therefore in an attachment. >>> >>> -- Forwarded message -- >>> From: Putowsky >>> To: Michael Ossipoff >>> Cc: sundial list >>> Bcc: >>> Date: Tue, 9 May 2017 21:49:58 +0200 >>> Subject: Re: Construction-Principle of Capuchin & Universal Capuchin >>> Dials??? >>> Here is the complete article. >>> >>> http://articles.adsabs.harvard.edu//full/1961JRASC..55...49S >>> /054.000.html >>> >>> putow...@yahoo.com >>> >>> On May 9, 2017, at 8:50 PM, Michael Ossipoff >>> wrote: >>> >>> I'm not asking about the *instructions *for constructing Capuchin and >>> Universal Capuchin dials. I'm asking about the principle, the explanation, >>> the justification, for their construction. >>> >>> Some websites have said or implied that it has to do with an >>> orthographic planisphere. I'm familiar with the use of a universal >>> planisphere, an azimuthal projection of the celestial sphere in >>> equatorial-aspect. ...but it isn't entirely clear how that relates to the >>> Capuchin dials. >>> >>> I found a handwaving explanation on the web. I've pasted its diagram, >>> and some of its "explanation", below in this e-mail. >>> >>> The explanation says that the diagram below, an orthographic projection >>> of the celestial-sphere, looks just like
Re: Capuchin and Regiomontanus dials
Fred-- Thanks for your answer. I'll look for Fuller's article. One or twice, I verified for myself, by analytic geometry, that the Universal Capuchin Dial agrees with the formula that relates altitude, time, declination and latitude. But that wasn't satisfying. Verifying a construction isn't the same as finding one. Without knowing in advance what the construction and use instructions are, I don't know of a way to design such a dial. ...or how the medieval astronomers and dialists arrived at it. But there's an exasperatingly tantalizing approach that gets partway. ...based on the formula for time in terms of altitude, latitude and declination: cos h = (sin alt - sin lat sin dec)/(cos dec cos lat) Dividing each term of the numerator by the denominator: cos h = sin alt/(cos dec cos lat) - tan lat tan dec If, in the drawing of the dial, the sun is toward the right, and you tip the device upward on the right side to point it at the sun, then the plum-line swings to the left, and the distance that the plum-bob moves to the left is the length of the thread (L) times sin alt. So that seems to account for the sin alt, at least tentatively. Constructing the dial, if you draw a horizontal line in from a point on the right-hand, side a distance L equal to the length of that thread, then draw a vertical line there, and then, from that side-point, draw lines angled upward by various amounts of latitude, then each line will meet the vertical line a distance of L tan lat, up from the first (horizonal) line. So the distance from the horizontal line, up the vertical line to a particular latitude-mark is L tan lat. At each latitude-mark, make a horizontal line. >From the bottom of that vertical line, where it meets the horizontal line, draw lines angled to the right from the vertical line by various amounts of declination. Draw them up through all the horizontal lines. Because a latitude-line is L tan lat above the original bottom horizontal line, then the distance to the right of the vertical line, at which one of the declination-lines meets that latitude-line is L tan lat tan dec. That's where we fix the upper end of the plumb-line. Then, when we tip the instrument up on the right, to point at the sun, and the plumb-bob swings, its distance to the left of the middle will be: sin alt - tan lat tan dec. That's starting to look like the formula. Maybe it would be simpler to just say that L is equal to 1. But we want sin alt/(cos lat cos dec). The instructions for using the Universal Capuchin dial talk about adjusting the distance of the bead from the top of the string before using the dial, and that's got to be how you change sin alt to sin alt/(cos lat cos dec). I guess I could study how that's done, by reading the construction and use instructions again. I guess you'd want to make the plumb-line's length equal to sec lat sec dec instead of 1. ...and there must be some way to achieve that by adjusting the bead by some constructed figure, as described in the use-instructions. But it isn't obvious to me how that would be done--especially if that bead-adjustment is to be done after fixing the top-end of the plumb-line in position. Maybe it would be easier if the bead-adjustment is done before fixing the top end of the plumb-line, so that you know where you'll be measuring from. I don't know. And then there's the matter of cos h. Just looking at afternoon... Because positive h is measured to the right from the meridian--afternoon---and because, the later the afternoon hour, the lower the sun is--then, in the afternoon, it seems to make sense for a larger bead-swing to the left to represent an earlier hour...an hour angle with a larger cosine. I guess, for afternoon, the vertical hour lines are positioned to the left of middle by distance proportional to the cosine of the hour-angle. - So, this isn't an explanation, but just a possible suggestion of the start of an explanation. Maybe it can become an explanation. But I still have no idea how an orthographic projection leads to the construction of the Universal Capuchin dial. (If a Capuchin dial isn't universal, it loses a big advantage over the Shepard's dial, or the related Roman Flat altitude dial.) Michael Ossipoff On Sat, May 13, 2017 at 3:47 PM, Fred Sawyer wrote: > Take a look at A.W. Fuller's article Universal Rectilinear Dials in the > 1957 Mathematical Gazette. He says: > > "I have repeatedly tried to evolve an explanation of some way in which > dials of this kind may have been invented. Only recently have I been > satisfied with my results." > > The rest of the article is dedicated to developing his idea. > > Note that it's only speculation - he can't point to any actual historical > proof. That's the problem with this whole endeavor; there is no
Re: Capuchin and Regiomontanus dials
When I said that the vertical hour-lines should be drawn at distance, to the left, from the middle vertical line, that is proportional to the cosine of the hour-angle... I should say *equal to* the cosine of the hour-angle, instead of proportional to it. ...where the length of the first horizontal line, from the right edge to the point where the vertical line is drawn, is one unit. Michael Ossipoff On Sat, May 13, 2017 at 7:03 PM, Michael Ossipoff wrote: > Fred-- > > Thanks for your answer. I'll look for Fuller's article. > > One or twice, I verified for myself, by analytic geometry, that the > Universal Capuchin Dial agrees with the formula that relates altitude, > time, declination and latitude. > > But that wasn't satisfying. Verifying a construction isn't the same as > finding one. Without knowing in advance what the construction and use > instructions are, I don't know of a way to design such a dial. > > ...or how the medieval astronomers and dialists arrived at it. > > But there's an exasperatingly tantalizing approach that gets partway. > ...based on the formula for time in terms of altitude, latitude and > declination: > > cos h = (sin alt - sin lat sin dec)/(cos dec cos lat) > > Dividing each term of the numerator by the denominator: > > cos h = sin alt/(cos dec cos lat) - tan lat tan dec > > If, in the drawing of the dial, the sun is toward the right, and you tip > the device upward on the right side to point it at the sun, then the > plum-line swings to the left, and the distance that the plum-bob moves to > the left is the length of the thread (L) times sin alt. > > So that seems to account for the sin alt, at least tentatively. > > Constructing the dial, if you draw a horizontal line in from a point on > the right-hand, side a distance L equal to the length of that thread, then > draw a vertical line there, and then, from that side-point, draw lines > angled upward by various amounts of latitude, then each line will meet the > vertical line a distance of L tan lat, up from the first (horizonal) line. > > So the distance from the horizontal line, up the vertical line to a > particular latitude-mark is L tan lat. > > At each latitude-mark, make a horizontal line. > > From the bottom of that vertical line, where it meets the horizontal line, > draw lines angled to the right from the vertical line by various amounts of > declination. Draw them up through all the horizontal lines. > > Because a latitude-line is L tan lat above the original bottom horizontal > line, then the distance to the right of the vertical line, at which one of > the declination-lines meets that latitude-line is L tan lat tan dec. > > That's where we fix the upper end of the plumb-line. Then, when we tip the > instrument up on the right, to point at the sun, and the plumb-bob swings, > its distance to the left of the middle will be: sin alt - tan lat tan dec. > > That's starting to look like the formula. > > Maybe it would be simpler to just say that L is equal to 1. > > But we want sin alt/(cos lat cos dec). > > The instructions for using the Universal Capuchin dial talk about > adjusting the distance of the bead from the top of the string before using > the dial, and that's got to be how you change sin alt to sin alt/(cos lat > cos dec). > > I guess I could study how that's done, by reading the construction and use > instructions again. > > I guess you'd want to make the plumb-line's length equal to sec lat sec > dec instead of 1. ...and there must be some way to achieve that by > adjusting the bead by some constructed figure, as described in the > use-instructions. > > But it isn't obvious to me how that would be done--especially if that > bead-adjustment is to be done after fixing the top-end of the plumb-line in > position. > > Maybe it would be easier if the bead-adjustment is done before fixing the > top end of the plumb-line, so that you know where you'll be measuring from. > I don't know. > > And then there's the matter of cos h. > > Just looking at afternoon... > > Because positive h is measured to the right from the > meridian--afternoon---and because, the later the afternoon hour, the lower > the sun is--then, in the afternoon, it seems to make sense for a larger > bead-swing to the left to represent an earlier hour...an hour angle with a > larger cosine. > > I guess, for afternoon, the vertical hour lines are positioned to the left > of middle by distance proportional to the cosine of the hour-angle. > > - > > So, this isn't an explanation, but just a possible suggestion of the start > of an explanation. >
Re: Capuchin and Regiomontanus dials
ontanus dial agrees with the formula that relates time, altitude, declination and latitude. That involved big (maybe page-filling, it seems to me) equations with lots of terms. When a proposition is proved in that way, that proof shows that the proposition is true, but it doesn't satisfyingly show why it's true, what makes it true. The naturally and obviously motivated construction that I've described here is much better in that regard. The only part that gets elaborately-calculated is the finding of that fortuitous, easy to do (but not easy to find) way to get the right thread-length with only one measurement, when the thread-end is already positioned for use. But, as I mentioned, the desired end-to-bead thread-length can be easily achieved by the obviously and naturally-motivated two-measurement method that I described above. Michael Ossipoff On Sat, May 13, 2017 at 9:23 PM, Michael Ossipoff wrote: > When I said that the vertical hour-lines should be drawn at distance, to > the left, from the middle vertical line, that is proportional to the cosine > of the hour-angle... > > I should say *equal to* the cosine of the hour-angle, instead of > proportional to it. > > ...where the length of the first horizontal line, from the right edge to > the point where the vertical line is drawn, is one unit. > > Michael Ossipoff > > > On Sat, May 13, 2017 at 7:03 PM, Michael Ossipoff > wrote: > >> Fred-- >> >> Thanks for your answer. I'll look for Fuller's article. >> >> One or twice, I verified for myself, by analytic geometry, that the >> Universal Capuchin Dial agrees with the formula that relates altitude, >> time, declination and latitude. >> >> But that wasn't satisfying. Verifying a construction isn't the same as >> finding one. Without knowing in advance what the construction and use >> instructions are, I don't know of a way to design such a dial. >> >> ...or how the medieval astronomers and dialists arrived at it. >> >> But there's an exasperatingly tantalizing approach that gets partway. >> ...based on the formula for time in terms of altitude, latitude and >> declination: >> >> cos h = (sin alt - sin lat sin dec)/(cos dec cos lat) >> >> Dividing each term of the numerator by the denominator: >> >> cos h = sin alt/(cos dec cos lat) - tan lat tan dec >> >> If, in the drawing of the dial, the sun is toward the right, and you tip >> the device upward on the right side to point it at the sun, then the >> plum-line swings to the left, and the distance that the plum-bob moves to >> the left is the length of the thread (L) times sin alt. >> >> So that seems to account for the sin alt, at least tentatively. >> >> Constructing the dial, if you draw a horizontal line in from a point on >> the right-hand, side a distance L equal to the length of that thread, then >> draw a vertical line there, and then, from that side-point, draw lines >> angled upward by various amounts of latitude, then each line will meet the >> vertical line a distance of L tan lat, up from the first (horizonal) line. >> >> So the distance from the horizontal line, up the vertical line to a >> particular latitude-mark is L tan lat. >> >> At each latitude-mark, make a horizontal line. >> >> From the bottom of that vertical line, where it meets the horizontal >> line, draw lines angled to the right from the vertical line by various >> amounts of declination. Draw them up through all the horizontal lines. >> >> Because a latitude-line is L tan lat above the original bottom horizontal >> line, then the distance to the right of the vertical line, at which one of >> the declination-lines meets that latitude-line is L tan lat tan dec. >> >> That's where we fix the upper end of the plumb-line. Then, when we tip >> the instrument up on the right, to point at the sun, and the plumb-bob >> swings, its distance to the left of the middle will be: sin alt - tan lat >> tan dec. >> >> That's starting to look like the formula. >> >> Maybe it would be simpler to just say that L is equal to 1. >> >> But we want sin alt/(cos lat cos dec). >> >> The instructions for using the Universal Capuchin dial talk about >> adjusting the distance of the bead from the top of the string before using >> the dial, and that's got to be how you change sin alt to sin alt/(cos lat >> cos dec). >> >> I guess I could study how that's done, by reading the construction and >> use instructions again. >> >> I guess you'd want to make the plumb-line&#
Re: Capuchin and Regiomontanus dials
Thanks, I'll check it out. I used to be put off from the altitude dials by the noon inaccuracy. I was concerned that Romans must have sometimes been late to noon appointments and lunch-dates. But I'd expect that, where lots of people are using altitude dials, punctuality-critical events and appointments wouldn't be scheduled for times near noon. Altitude dials have the advantage that they combine a sundial with a built-in indication of what time the sun will set. Also, the polar-style dials, which need to be oriented by compass, or two different kinds of dial (like a polar-style dial and an analemmatic dial) on the same instrument, or a declination-measurement being correct--They might be more demanding on the person using the dial, because it's necessary to watch the compass, the declination-reading, or the time-match of the two dials. ...So it seems as if an altitude dial might be easier to use. And the pre-adjustable ones seem likely to be easier to use than a Shepard's dial or Roman Flat altitude dial, with which you have to be concerned that the gnomon-point-shadow is on right date's point on the lines. But I've used compass tablet-dials, and mine were all accurate within 5 minutes, and one was usually accurate within 3 minutes. I like the Marke dial too. I think you wrote an article about it in Compendium. But if I were to make a universal portable altitude dial for someone, I think they'd prefer the easier declination and latitude adjustment of the Regiomontanus dial. The only sundials I've made have been those compass tablet-dials, but if I have reason to make another portable dial, it will be an altitude dial. Well, I might, at some time, make the Regiomontanus, Marke and Ring-Equinoctical dials, just to find out what it's like to make and use them, and to show them to my girlfriend. I have a clever folded-cardboard version of the ring-equinoctical, from a cut-out pattern in a book. It's on a 2X1 shaped cardboard, folded at the middle to a right-angle, with a thread to limit it to that angle. A quarter-circle of an equatorial sundial-scale is printed on the surfaces, like a quarter of a Disk-Equatorial. An edge serves as the polar style, A string-plumbline, used with one of the degree-scales, facilitates the correct vertical tip, for the polar-gnomon. Or one of the printed degree-scales can be used for vertical orientation by sighting on the horizon, if the horizon is visible. A small paper tab, sliding on one of the edges, and casting an edge-shadow on a date-scale, gives a declination-reading that can be used to azimuth-orient the dial. Michael Ossipoff On Sun, May 14, 2017 at 5:18 PM, Fred Sawyer wrote: > Michael, > > See the attached slide from my talk. All the various dials work with a > string of this length. They vary simply in where the suspension point is > placed. The pros and cons of the various suspension points were part of my > presentation. > > Fred Sawyer > > > On Sun, May 14, 2017 at 4:40 PM, Michael Ossipoff > wrote: > >> When I said that there isn't an obvious way to measure to make the >> plumb-line length equal to sec lat sec dec, I meant that there' s no >> obvious way to achieve that *with one measurement*. >> >> I was looking for a way to do it with one measurement, because that's how >> the use-instructions say to do it. >> >> In fact, not only is it evidently done with one measurement, but that one >> measurement has the upper end of the plumb-line already fixed to the point >> from which it's going to be used, at the intersection of the appropriate >> latitude-line and declination-line. >> >> That's fortuitous, that it can be done like that, with one measurement, >> and using only one positioning of the top end of the plumb-line. >> >> But of course it's easier, (to find) and there's an obviously and >> naturally-motivated way to do it, with *two* measurements, before fixing >> the top-end of the plumb-line at the point where it will be used. >> >> The line from that right-edge point (from which the first horizontal is >> drawn) to the point where the appropriate latitude-line intersects the >> vertical has a length of sec lat. >> >> So, before fixing the top end of the plumb-line where it will be used >> from, at the intersection of the appropriate lat and dec lines, just place >> the top end of the plumb line at one end of that line mentioned in the >> paragraph before this one, and slide the bead to the other end of that >> line. ...to get a length of thread equal to sec lat. >> >> Then, have a set of declination marks at the right edge, just like the >> ones that are actually on a Regiomontanus dial, except that the lines from >
Re: Capuchin and Regiomontanus dials
Thanks for the Regiomontanus slide. Then the original designer of that dial must have just checked out the result of that way of setting the bead, by doing the calculation to find out if squrt((1+tan dec tan lat)^2 + (tan dec - tan lat)^2)) = sec lat sec dec, as a trial-and error trial that? Or, I don't know, is that a trigonometric fact that would be already known to someone who is really experienced in trig? --- What's the purpose of the lower latitude scale, on the dial shown in that slide? When I described my folded-cardboard portable equatorial-dial, I mis-stated the declination arrangement: Actually, the sliding paper tab (made by making two slits in the bottom of the tab, and fitting that onto an edge of the cardboard) is positioned via date-markngs along that edge. The declination reading, and therefore the azimuth, is correct when the shadow of a certain edge of the tab, perpendicular to the cardboard edge on which it slides, just reaches the hour-scale on the surface that's serving as a quarter of an Disk-Equatorial dial. Actually, that dial was intended as an emergency backup at sea, where there would always be available a horizon by which to vertically orient the dial. The use of a plumb-bob for that purpose was my idea, because, on land there often or usually isn't a visible horizon, due to houses, trees, etc. Maybe, in really flat land, even without an ocean horizon, even a land-horizon could be helpful, but such a horizon isn't usually visible in most places on land. But then, with the plumb-line, it's necessary to keep the vertical surface parallel to the pendulum-string, and keep the pendulum-string along the right degree-mark, while making sure that the declination-reading is right, when reading the time. ...Four things to keep track of at the same time. ...maybe making that the most difficult-to-use portable dial. With the Equinoctical Ring-Dial, the vertical orientation, about both horizontal axes, is automatically achieved by gravity, so only time and declination need be read. And, with a pre-adjustable altitude-dial, only the sun-alignment shadow and the time need to be read. With my compass tablet-dials, one mainly only had to watch the compass and the time-reading. Of course it was necessary to hold the dial horizontal, without a spirit-level, but that didn't keep them from being accurate. Michael Ossipoff On Sun, May 14, 2017 at 5:18 PM, Fred Sawyer wrote: > Michael, > > See the attached slide from my talk. All the various dials work with a > string of this length. They vary simply in where the suspension point is > placed. The pros and cons of the various suspension points were part of my > presentation. > > Fred Sawyer > > > On Sun, May 14, 2017 at 4:40 PM, Michael Ossipoff > wrote: > >> When I said that there isn't an obvious way to measure to make the >> plumb-line length equal to sec lat sec dec, I meant that there' s no >> obvious way to achieve that *with one measurement*. >> >> I was looking for a way to do it with one measurement, because that's how >> the use-instructions say to do it. >> >> In fact, not only is it evidently done with one measurement, but that one >> measurement has the upper end of the plumb-line already fixed to the point >> from which it's going to be used, at the intersection of the appropriate >> latitude-line and declination-line. >> >> That's fortuitous, that it can be done like that, with one measurement, >> and using only one positioning of the top end of the plumb-line. >> >> But of course it's easier, (to find) and there's an obviously and >> naturally-motivated way to do it, with *two* measurements, before fixing >> the top-end of the plumb-line at the point where it will be used. >> >> The line from that right-edge point (from which the first horizontal is >> drawn) to the point where the appropriate latitude-line intersects the >> vertical has a length of sec lat. >> >> So, before fixing the top end of the plumb-line where it will be used >> from, at the intersection of the appropriate lat and dec lines, just place >> the top end of the plumb line at one end of that line mentioned in the >> paragraph before this one, and slide the bead to the other end of that >> line. ...to get a length of thread equal to sec lat. >> >> Then, have a set of declination marks at the right edge, just like the >> ones that are actually on a Regiomontanus dial, except that the lines from >> the intersection of the first horizontal and vertical lines, to the >> declination (date) marks at the right-margins are shown. >> >> Oh, but have that system of lines drawn a bit larger
Re: Capuchin and Regiomontanus dials
I asked: "Or, I don't know, is that a trigonometric fact that would be already known to someone who is really experienced in trig?" Well, alternative expressions for the product of two cosines is something that might be basic and frequently-occurring enough to be written down somewhere, where someone could look it up. Maybe someone who'd thoroughly studied trig, and done a lot of it, would know it without looking it up. It might be especially notable that one of the alternative expressions for sec x sec y is the square-root of the sum of two squares, a Pythagorean distance. Michael Ossipoff On Mon, May 15, 2017 at 11:32 AM, Michael Ossipoff wrote: > Thanks for the Regiomontanus slide. > > Then the original designer of that dial must have just checked out the > result of that way of setting the bead, by doing the calculation to find > out if > squrt((1+tan dec tan lat)^2 + (tan dec - tan lat)^2)) = sec lat sec dec, > as a trial-and error trial that? > > Or, I don't know, is that a trigonometric fact that would be already known > to someone who is really experienced in trig? > > --- > > What's the purpose of the lower latitude scale, on the dial shown in that > slide? > > > > When I described my folded-cardboard portable equatorial-dial, I > mis-stated the declination arrangement: > > Actually, the sliding paper tab (made by making two slits in the bottom of > the tab, and fitting that onto an edge of the cardboard) is positioned via > date-markngs along that edge. The declination reading, and therefore the > azimuth, is correct when the shadow of a certain edge of the tab, > perpendicular to the cardboard edge on which it slides, just reaches the > hour-scale on the surface that's serving as a quarter of an Disk-Equatorial > dial. > > Actually, that dial was intended as an emergency backup at sea, where > there would always be available a horizon by which to vertically orient the > dial. > > The use of a plumb-bob for that purpose was my idea, because, on land > there often or usually isn't a visible horizon, due to houses, trees, etc. > Maybe, in really flat land, even without an ocean horizon, even a > land-horizon could be helpful, but such a horizon isn't usually visible in > most places on land. > > But then, with the plumb-line, it's necessary to keep the vertical surface > parallel to the pendulum-string, and keep the pendulum-string along the > right degree-mark, while making sure that the declination-reading is right, > when reading the time. > > ...Four things to keep track of at the same time. ...maybe making that > the most difficult-to-use portable dial. > > With the Equinoctical Ring-Dial, the vertical orientation, about both > horizontal axes, is automatically achieved by gravity, so only time and > declination need be read. > > And, with a pre-adjustable altitude-dial, only the sun-alignment shadow > and the time need to be read. > > With my compass tablet-dials, one mainly only had to watch the compass and > the time-reading. Of course it was necessary to hold the dial horizontal, > without a spirit-level, but that didn't keep them from being accurate. > > Michael Ossipoff > > > > On Sun, May 14, 2017 at 5:18 PM, Fred Sawyer wrote: > >> Michael, >> >> See the attached slide from my talk. All the various dials work with a >> string of this length. They vary simply in where the suspension point is >> placed. The pros and cons of the various suspension points were part of my >> presentation. >> >> Fred Sawyer >> >> >> On Sun, May 14, 2017 at 4:40 PM, Michael Ossipoff > > wrote: >> >>> When I said that there isn't an obvious way to measure to make the >>> plumb-line length equal to sec lat sec dec, I meant that there' s no >>> obvious way to achieve that *with one measurement*. >>> >>> I was looking for a way to do it with one measurement, because that's >>> how the use-instructions say to do it. >>> >>> In fact, not only is it evidently done with one measurement, but that >>> one measurement has the upper end of the plumb-line already fixed to the >>> point from which it's going to be used, at the intersection of the >>> appropriate latitude-line and declination-line. >>> >>> That's fortuitous, that it can be done like that, with one measurement, >>> and using only one positioning of the top end of the plumb-line. >>> >>> But of course it's easier, (to find) and there's an obviously and >>> naturally-motivated way to do it, wit
Re: Capuchin and Regiomontanus dials
Wow. What can I say. Your approach makes more sense in every way, than the way that I'd been trying to find how the bead-setting procedure could have been arrived at. I'd wanted to start with various pairs of points, and then find out if any of them are separated by a distance of sec lat sec dec. But of course (now it's obvious) it makes a lot more sense to start with sec lat sec dec, and find out if it can be made into a distance. ...which is of course how you approached the problem. If we expect the distance on the dial to be a diagonal distance, then it will be the sum of two squares, all in a square-root sign. Most likely it will be a diagonal distance, which means the it will be the sum of two squares, all in a square-root sign. Of course it _needn't_ be a diagonal distance. It could be all horizontal or all vertical. But, a lot of distances already on the dial are expressed as tangents, and more could be. So, converting the sec to tan makes sense, for a start. The familiar identity that relates sec and tan involves their squares. That suggests a diagonal distance, adding some confirmation to the initial impression that a diagonal distance might be more likely. So (tan lat + 1) and (tan dec + 1) are multiplied together, resulting in four terms, each of which is a square (...though of course the 1 needn't snecessrily have been gotten by squaring--except that it wasn't gotten by multiplying other numbers. So maybe it should be considered a square). The fact that there are four squares suggests that the two squared expressions are both binomials. ...and that the squares' middle terms cancel eachother out. (Of course maybe the inventor didn't have a way to be sure that sec lat sec dec can be written as a distance on the dial at all. But, if not, he evidently checked out the possibility.) So, if the four squares are the squares of the terms of two binomials, with their middle terms canceling out, there are 3 ways in which the two binomials could be assembled from the square roots of those four squares. In a way, it doesn't matter which way it's done, as long as it results in a distance. But, for that diagonal distance, of course it's necessary that the two squared binomials reapresnt distances in mutually perpendicular directions. Well there's an obvious distance there, among the square-roots of those terms: tan lat tan dec. It's horizontal, and is the distance of the string-hang-point forward (sunward) from the middle vertical. And if the 1 is added to it, that's the horizontal distance of the string-hang-point from the rear edge of the dial-card. Of the square-roots of the other two terms, tan lat is the vertical distance of the string-hang point above the main horizontal, the first horizontal. So that works--a horizontal distance and a vertical distance, which are needed for a diagonal distance. And of course naturally (tan lat - tan dec) would be a vertical distance from the string-hang-point, to the upper-end of a line has been drawn across half the dial-card's 2-unit width, one end on the first horizontal, with the line angled up by the declination-angle. Since the horizontal distance suggested was from the string-hang-point to the rear edge of the dial, and because the string-hang point is tan lat above the first horizontal, then that suggests that the measurement should be from the string-hang point, to a point that is tan dec above the first horizontal, on the rear margin of the dial. ...leading to the Regiomontanus's way of setting the bead. And, in that way, that beat-setting method is naturally arrived at. So thanks for pointing out that natural approach, making choices than make more sense than the approach I was considering. Michael Ossipoff On Mon, May 15, 2017 at 2:54 PM, Geoff Thurston wrote: > Michael, > > I seem to recall that sec^2(x)=1+tan^2(x) > > Therefore sec^2(lat).sec^2(dec)=(1+tan^2(lat)).(1+tan^2(dec)) > > =1+tan^2(lat)+tan^2(dec)+tan^2(lat).tan^2(dec) > > =(1+tan dec tan lat)^2 + (tan dec - tan lat)^2 > > I guess that this relationship, which is just a variant of sin^2+cos^2=1, > should have been known to the dial designer. > > Geoff > > On 15 May 2017 at 16:32, Michael Ossipoff wrote: > >> Thanks for the Regiomontanus slide. >> >> Then the original designer of that dial must have just checked out the >> result of that way of setting the bead, by doing the calculation to find >> out if >> squrt((1+tan dec tan lat)^2 + (tan dec - tan lat)^2)) = sec lat sec dec, >> as a trial-and error trial that? >> >> Or, I don't know, is that a trigonometric fact that would be already >> known to someone who is really experienced in trig? >> >> --- >> >> What's the purpose of the lower latitude scale, on the dial s
Re: Capuchin and Regiomontanus dials
Of course, because only the four squared-terms are present, the two binomials have to be chosen so that, when they're both squared, their resulting middle terms cancel eachother out. (tan lat tan dec + 1) and (tan lat - tan dec) meet that requirement. Michael Ossipoff On Mon, May 15, 2017 at 9:25 PM, Michael Ossipoff wrote: > Wow. What can I say. > > Your approach makes more sense in every way, than the way that I'd been > trying to find how the bead-setting procedure could have been arrived at. > > I'd wanted to start with various pairs of points, and then find out if any > of them are separated by a distance of sec lat sec dec. > > But of course (now it's obvious) it makes a lot more sense to start with > sec lat sec dec, and find out if it can be made into a distance. ...which > is of course how you approached the problem. > > If we expect the distance on the dial to be a diagonal distance, then it > will be the sum of two squares, all in a square-root sign. > > Most likely it will be a diagonal distance, which means the it will be the > sum of two squares, all in a square-root sign. > > Of course it _needn't_ be a diagonal distance. It could be all horizontal > or all vertical. But, a lot of distances already on the dial are expressed > as tangents, and more could be. So, converting the sec to tan makes sense, > for a start. > > The familiar identity that relates sec and tan involves their squares. > That suggests a diagonal distance, adding some confirmation to the initial > impression that a diagonal distance might be more likely. > > So (tan lat + 1) and (tan dec + 1) are multiplied together, resulting in > four terms, each of which is a square (...though of course the 1 needn't > snecessrily have been gotten by squaring--except that it wasn't gotten by > multiplying other numbers. So maybe it should be considered a square). > > The fact that there are four squares suggests that the two squared > expressions are both binomials. ...and that the squares' middle terms > cancel eachother out. > > (Of course maybe the inventor didn't have a way to be sure that sec lat > sec dec can be written as a distance on the dial at all. But, if not, he > evidently checked out the possibility.) > > So, if the four squares are the squares of the terms of two binomials, > with their middle terms canceling out, there are 3 ways in which the two > binomials could be assembled from the square roots of those four squares. > > In a way, it doesn't matter which way it's done, as long as it results in > a distance. But, for that diagonal distance, of course it's necessary that > the two squared binomials reapresnt distances in mutually perpendicular > directions. > > Well there's an obvious distance there, among the square-roots of those > terms: tan lat tan dec. It's horizontal, and is the distance of the > string-hang-point forward (sunward) from the middle vertical. And if the 1 > is added to it, that's the horizontal distance of the string-hang-point > from the rear edge of the dial-card. > > Of the square-roots of the other two terms, tan lat is the vertical > distance of the string-hang point above the main horizontal, the first > horizontal. > > So that works--a horizontal distance and a vertical distance, which are > needed for a diagonal distance. And of course naturally (tan lat - tan dec) > would be a vertical distance from the string-hang-point, to the upper-end > of a line has been drawn across half the dial-card's 2-unit width, one end > on the first horizontal, with the line angled up by the declination-angle. > > Since the horizontal distance suggested was from the string-hang-point to > the rear edge of the dial, and because the string-hang point is tan lat > above the first horizontal, then that suggests that the measurement should > be from the string-hang point, to a point that is tan dec above the first > horizontal, on the rear margin of the dial. > > ...leading to the Regiomontanus's way of setting the bead. > > And, in that way, that beat-setting method is naturally arrived at. > > So thanks for pointing out that natural approach, making choices than make > more sense than the approach I was considering. > > Michael Ossipoff > > > > > > > > > On Mon, May 15, 2017 at 2:54 PM, Geoff Thurston > wrote: > >> Michael, >> >> I seem to recall that sec^2(x)=1+tan^2(x) >> >> Therefore sec^2(lat).sec^2(dec)=(1+tan^2(lat)).(1+tan^2(dec)) >> >> =1+tan^2(lat)+tan^2(dec)+tan^2(lat).tan^2(dec) >> >> =(1+tan dec tan lat)^2 + (tan dec - tan lat)^2 >> >> I guess that this relationship, wh
Re: Capuchin and Regiomontanus dials
On Sun, May 14, 2017 at 5:18 PM, Fred Sawyer wrote: > Michael, > > See the attached slide from my talk. All the various dials work with a > string of this length. They vary simply in where the suspension point is > placed. The pros and cons of the various suspension points were part of my > presentation. > What were some of the alternatives, and some of their relative advantages? Michael Ossipoff > > > Fred Sawyer > > > On Sun, May 14, 2017 at 4:40 PM, Michael Ossipoff > wrote: > >> When I said that there isn't an obvious way to measure to make the >> plumb-line length equal to sec lat sec dec, I meant that there' s no >> obvious way to achieve that *with one measurement*. >> >> I was looking for a way to do it with one measurement, because that's how >> the use-instructions say to do it. >> >> In fact, not only is it evidently done with one measurement, but that one >> measurement has the upper end of the plumb-line already fixed to the point >> from which it's going to be used, at the intersection of the appropriate >> latitude-line and declination-line. >> >> That's fortuitous, that it can be done like that, with one measurement, >> and using only one positioning of the top end of the plumb-line. >> >> But of course it's easier, (to find) and there's an obviously and >> naturally-motivated way to do it, with *two* measurements, before fixing >> the top-end of the plumb-line at the point where it will be used. >> >> The line from that right-edge point (from which the first horizontal is >> drawn) to the point where the appropriate latitude-line intersects the >> vertical has a length of sec lat. >> >> So, before fixing the top end of the plumb-line where it will be used >> from, at the intersection of the appropriate lat and dec lines, just place >> the top end of the plumb line at one end of that line mentioned in the >> paragraph before this one, and slide the bead to the other end of that >> line. ...to get a length of thread equal to sec lat. >> >> Then, have a set of declination marks at the right edge, just like the >> ones that are actually on a Regiomontanus dial, except that the lines from >> the intersection of the first horizontal and vertical lines, to the >> declination (date) marks at the right-margins are shown. >> >> Oh, but have that system of lines drawn a bit larger, so that the origin >> of the declination-lines to the right margin is a bit farther to the left >> from the intersection of the first horizontal and the first vertical. >> ...but still on a leftward extension of the first horizontal. >> >> That's so that there will be room for the 2nd measurement, the >> measurement that follows. >> >> And have closely spaced vertical lines through those diagonal >> declination-lines to the right margin. >> >> So now lay the thread-length that you've measured above, along the first >> horizontal, with one end at the origin of the declination-lines to the >> margin. >> Note how far the thread reaches, among the closely-spaced vertical lines >> through those margin declination-lines. >> >> Now measure, from the origin of the margin declination-lines along the >> appropriate margin declination-line, to that one of the closely-spaced >> vertical lines that the thread reached in the previous paragraph. >> >> With the left end of the thread at the origin of the margin >> declination-lines, slide the bead along the thread to that vertical line. >> >> That will give a thread length, from end to bead, of sec lat sec dec. >> >> ...achieved in the easy (to find) way, by two measurements, before fixing >> the thread (plumb-line) end to the point from which it will be used. >> >> I wanted to mention that way of achieving that end-to-bead thread-length, >> to show that it can be easily done, and doesn't depend on the fortuitous >> way that's possible and used by the actual Regiomontanus dial, whereby only >> one thread-length measurement is needed, and the only positioning of the >> thread-end is at the point from which it will be used. >> >> Having said that, I suppose it would be natural for someone to look for >> a fortuitous way that has the advantages mentioned in the paragraph before >> this one. >> >> And I suppose it would be natural to start the trial-and-error search >> from the thread-end position where the thread will eventually be used, to >> have the advantage of only one thread-end positioning. >> >> One would wri
Re: Cast resin sundial
Hi Dan-- I don't claim to have an answer to your question, because (evidently like most) I don't know anything about casting resin. At least one 5-face cube-dial, or 4-face pillar dial is on my to-do list. I like them because they're readable at relatively long distance, from all directions, and useful at all times of day. Also, with a nodus for declination, or co-Italian or Babylonian hours, there'd nearly always be one of the faces on which the nodus's shadow is on the dial-face. A multi-face dial is the answer to the problem of a nudus-shadow not always being on the dial-face. Aside from that, cube-dials are attractive, decorative, and interesting. A declining cube-dial has the advantage that all of its faces have their French hours style intersecting the dial-face, thereby telling time whenever the face receives sunlight. Also, all of its dials can have the same kind of oblique triangular gnomon (not the kind whose style is parallel to the dial-face), making for better and more consistent appearance. A cube-dial with one of its face's normal (perpendicular line) facing horizontal and due-north, or such a dial rotated only about its east-west axis, has the advantage of being easily explained to people--a consideration that I value. I once bought a resin sundial. I liked its realistic weight, heat-capacity, and feel, which, to me, seemed to passably resemble stone. But it was one of those affordable commercial sundials, all of which are completely unacceptably inaccurate and carelessly made &/or designed. It ended up breaking. I don't remember how. Maybe that was avoidable and my fault. Maybe I dropped it or stepped on it. My pillar dial will (if i make it) will consist of a wooden box, to be mounted on the middle of a vertical post. It will have holes in its top and bottom, to fit the post, and will be hinged along one vertical edge to close onto the post, with the holes lined with some soft material to grip the post without damaging it, and a bolt-&-wingnut on the edge opposite the hinge, to tighten the box-closure onto the post. It will have dials on its 4 vertical sides. Michael Ossipoff On Thu, May 25, 2017 at 1:30 PM, Dan-George Uza wrote: > Hello! > > I'm looking for advice on how to cast a sundial from epoxy resins, > specifically a cubical multiple sundial. Any ideas on how to go about > casting the faces? > > Thanks, > > Dan Uza > > --- > https://lists.uni-koeln.de/mailman/listinfo/sundial > > > --- https://lists.uni-koeln.de/mailman/listinfo/sundial
Re: Cast resin sundial
I should clarify what I meant by: "A cube-dial with one of its face's normal (perpendicular line) facing horizontal and due-north, or such a dial rotated only about its east-west axis, has the advantage of being easily explained to people--a consideration that I value." I meant that if two of the cube's dial-faces are facing directly east and west, then the construction of the French hour-lines for that cube-dial is easier to explain. So it's a trade-off between the easier explainability of the cube aligned in that way, vs the better appearance, and better hours-coverage on all dial-faces, of a declining cube-dial. ...better hours coverage because, on every dial, the style intersects the dial-face surface, telling time whenever the dial-face receives sunshine. ...better looks because all of the cube's dials have a similar gnomon whose style isn't parallel to the dial-face. Michael Ossipoff On Tue, Jun 6, 2017 at 7:59 PM, Michael Ossipoff wrote: > Hi Dan-- > > I don't claim to have an answer to your question, because (evidently like > most) I don't know anything about casting resin. > > At least one 5-face cube-dial, or 4-face pillar dial is on my to-do list. > I like them because they're readable at relatively long distance, from all > directions, and useful at all times of day. > > Also, with a nodus for declination, or co-Italian or Babylonian hours, > there'd nearly always be one of the faces on which the nodus's shadow is on > the dial-face. A multi-face dial is the answer to the problem of a > nudus-shadow not always being on the dial-face. > > Aside from that, cube-dials are attractive, decorative, and interesting. > > A declining cube-dial has the advantage that all of its faces have their > French hours style intersecting the dial-face, thereby telling time > whenever the face receives sunlight. > > Also, all of its dials can have the same kind of oblique triangular gnomon > (not the kind whose style is parallel to the dial-face), making for better > and more consistent appearance. > > A cube-dial with one of its face's normal (perpendicular line) facing > horizontal and due-north, or such a dial rotated only about its east-west > axis, has the advantage of being easily explained to people--a > consideration that I value. > > I once bought a resin sundial. I liked its realistic weight, > heat-capacity, and feel, which, to me, seemed to passably resemble stone. > But it was one of those affordable commercial sundials, all of which are > completely unacceptably inaccurate and carelessly made &/or designed. It > ended up breaking. I don't remember how. Maybe that was avoidable and my > fault. Maybe I dropped it or stepped on it. > > My pillar dial will (if i make it) will consist of a wooden box, to be > mounted on the middle of a vertical post. It will have holes in its top and > bottom, to fit the post, and will be hinged along one vertical edge to > close onto the post, with the holes lined with some soft material to grip > the post without damaging it, and a bolt-&-wingnut on the edge opposite the > hinge, to tighten the box-closure onto the post. It will have dials on its > 4 vertical sides. > > Michael Ossipoff > > > > On Thu, May 25, 2017 at 1:30 PM, Dan-George Uza > wrote: > >> Hello! >> >> I'm looking for advice on how to cast a sundial from epoxy resins, >> specifically a cubical multiple sundial. Any ideas on how to go about >> casting the faces? >> >> Thanks, >> >> Dan Uza >> >> --- >> https://lists.uni-koeln.de/mailman/listinfo/sundial >> >> >> > --- https://lists.uni-koeln.de/mailman/listinfo/sundial
Re: Golden Ratio and Sundials
On Wed, Jun 21, 2017 at 5:27 PM, Brooke Clarke wrote: > Hi Roderick: > > I also have a book on this number that makes the case that there is no > such ratio. > Your book is mistaken. If A/B = (A+B)/A, then A/B is the golden ratio. If a line-segment is divided into two parts related by that ratio, then the golden ratio is also called the golden section. If the interval between two numbers is divided into two intervals related by the golden ratio, then the golden ratio is also called the golden mean. > For example if you look at a photograph of something where do you put the > markers to make the measurement? > Along two mutually-perpendicular edges, measured from a common corner? :^) Michael Ossipoff > Brooke > Clarkehttp://www.PRC68.comhttp://www.end2partygovernment.com/2012Issues.html > > Original Message > > Hi all, > > I have been reading a book on the Golden Ratio which is 1.6180339887. It > describes how the Golden Ratio describes how the spiral of a sea shell is > produced. And how nature uses the Golden Ratio on the size of leaves etc. > > Does anyone know if sundials have ever been produced useing the Golden > Ratio. The Golden Ratio goes back in history so one wonders if it was ever > applied to sundials. > > The book describes that the short and long sizes of credit cards are close > to being the Golden Ratio. > > LongSide/ShortSide = Golden Ratio. > > Regards, > > Roderick Wall. > > > > ---https://lists.uni-koeln.de/mailman/listinfo/sundial > > > > --- > https://lists.uni-koeln.de/mailman/listinfo/sundial > > > --- https://lists.uni-koeln.de/mailman/listinfo/sundial
Re: Hemicyclium correction
On Mon, Oct 16, 2017 at 8:48 AM, Brad Thayer wrote: > I am looking to make a hemicyclium-type sundial (half-hemisphere) in a > metal working class. What little I can find on them says they are > inaccurate, without being very clear on the problem. > But the way, I've seen it spelled "Hemicycleum" as well. I don't know which is correct, but "Hemicycleum" looks better, it seems to me. But I'll use your spelling. It's probably better-accpeted. Whoever said that was mistaken. Hemicyclia are as in principle as accurate as any sundial can be. In ancient times, Hemicyclia were devised, instead of our modern polar-gnomon garden sundial, or our equatorial sundials, because in those days, they weren't using our Equal-Hours for civil time (Astronomers used it though). They were using "Temporary Hours), that divided each day into 12 equal hours, for their civil time. To achieve that, they used a stick-tip nodus or bead-nodus. to cast a point-shadow on the hemicyclium surface. As the Sun's declination changes seasonally, of course the tip-nodus's path on the hemicyclium changes too. So the hour-lines were curves, drawn so that, for any particular solar declination, those marks divide the day (sunrise to sunset) into 12 equal parts. As you can imagine, that makes the dial more complicated than modern ones. "Early" doesn't always mean "simpler". ...and so there was much opportunity for error in the calclulations and drafting,for those curved hour-lines. So maybe some hemicyclia *were* inaccurately drafted. For one thing, of course the exact time of day wasn't as crucial in those days, and of course the more precisely made, and prestigiously made, a sundial was, the more it was likely to cost. But there's no reason why your hemicyclium should be made for Temporary Hours. Make it for our modern Equal-Hours, also referred to as Local True Solar Time (LTST). > It appears to me the only issue is it needs to be tilted so that the > gnomon aligns with the Earth’s rotation axis; > The equinox circle on the Hemicyclium, the line that the tip-nodus follows on the day of the equinox, should be a circle parallel to the celestial equator. And yes, if you're going to use a polar gnomon instead of a tip-nodus, then that polar gnomon should be parallel to the Earth's axis, pointed at the north celestial pole. ...and should go through the center of the sphere from which the Hemicyclium is cut. But, if you're going to do that, then why make it a Hemicyclium? Why not just a Band-Equatorial dial? You could mount a cylindrical brass band, parallel to the equator, with a polar-parallel rod-gnomon mounted to go through the central axis of that band. You could mount that brass Band-Equatorial on a mount of whatever kind. For extra durability, you could mount it inside a concrete structure resembling a Hemicyclium. The durability of a Hemicyclium, with the simplicity and modernity of a Band-Equatorial. So then the hour-lines would just be polar-parallel lines equidistantly drawn along the inside of the band, dividing the lower half of the band into 12 equal parts. Of course you'd want half-hour lines too. Maybe, if you want it to be fancier and more accurate, you could divide each hour, instead, into 3, 4, or even 6 parts. ...depending on how much precision and work you want. But that's a lot of work. There's a good reason why the garden-style Horizontal-Dial is the most popular design for a stationary dial-- 1. It's easy to construct. 2. It tells the time whenever the sun is up (a Hemicyclium can do that too). 3. Unlike a Hemicyclium, a Horizontal-Dial is readable from all directions, provided that you're close enough to look at it from above. I'd say, forget about the analemic-edge gnomon. For one thing, that of course hugely complicates the design and construction. For another thing, if someone wants clock time, they can look at a clock or watch. A sundial should give sundial time, Local True Solar Time. You can have a nearby plaque-chart that tells the corrections, what to add to the sundial's time, to give the Standard-Time for your time-zone at various times of year.. ...and a reminder to add an hour for DaylightSavingTime, between the specified dates. I'd make the sundial for Local True Solar Time, equal-hours, instead of for Temporary Hours, because, not only is that easier, but it's also the basis Standard-Time (when adjusted for Equation-of-Time and for your longitude). I'd suggest changing your project to a garden-style Horizontal-Dial. Michael Ossipoff > > > --- https://lists.uni-koeln.de/mailman/listinfo/sundial
Re: Hemicyclium correction
But, if you're willing to give up the Horizontal-Dial's advantages, then an Equatorial-Dial has the following advantages: 1. Its equally-spaced hour-lines allow perfectly accurate linear interpolation of the time, when the shadow is between hour-lines. (But, when usiing pocket horizontal tablet-dials, linear interpolation gave results accurate with 3 minutes, when only the hours and half-hours were marked. So interpolation with unequally-spaced hour-lines doesn't seem a problem.) 2. Its principle is obvious. The Horizontal-Dial's construction-principle isn't difficult to explain, but the Equatorial's construction-principle is obvious at a glance. It would make perfect sense to anyone, without any explanation. (By the way, it's true that a Bifilar Dial shares the advantage of equally-spaced hour-lines. But it only tells time for part of the day, because, when the Sun is low, the shadow of interest won't be on the dial-plate.) Of course a two-sided Disk-Equatorial is incomparably easier to construct than a Band-Equatorial or Cylinder-Equatorial. ...if you don't mind the fact that a Disk-Equatorial can only be read from the north in the summer, and from the south in the winter. Michael Ossipoff On Mon, Oct 16, 2017 at 8:48 AM, Brad Thayer wrote: > I am looking to make a hemicyclium-type sundial (half-hemisphere) in a > metal working class. What little I can find on them says they are > inaccurate, without being very clear on the problem. It appears to me the > only issue is it needs to be tilted so that the gnomon aligns with the > Earth’s rotation axis; thus the half-bowl faces south and the gnomon points > south, but the end of the gnomon that attaches to the bowl points north. > Am I missing anything? I am also looking to use an analemma-shaped gnomon > to cast the shadow on the bowl, and at least month lines for the solar > elevation. The bowl will also have a rod and bracket on the bottom to > allow it to be rotated for daylight-savings time and for local longitude > corrections. > > > > Thanks in advance -- Brad > > --- > https://lists.uni-koeln.de/mailman/listinfo/sundial > > > --- https://lists.uni-koeln.de/mailman/listinfo/sundial
Re: Hemicyclium correction
When I have a clock and not a sundial, clock time has to be converted into sundial time (Local True Solar Time) to make it day-relevant. So, if you make a sundial, shouldn't it just show sundial time? Isn't that really what a sundial for--showing Local True Solar Time? You could make a correction-table to convert sundial-time to clock-time--consisting of the EoT, with the longitude-correction added to it for converting from sundial time to clock time. ...and display it beside the sundial. By the way, when I said that a Disk Equatorial is incomparably easier to make than a Band or Cylinder Equatorial, of course should have added "...unless you already have a cylinder or a band, and a means to make a hole in it, to make a circumference hole-nodus. Of course such a dial can only show 12 hours of time, but that can be remedied by having more than one circumference-hole nodus. I don't know the right terminology for what I call a Band-Equatorial or a Cylinder-Equatorial. If the band is wide enough for a circumference hole-nodus to cast it light-spot on the band all year, so that the band has a width equal to D*2tan(obliquity), giving it a width nearly equal to half its diameter, maybe that's the practical-difference-point at which a Band-Equatorial becomes a Cyllinder-Equatorial. As I understand it, "Equatorial Dial" usually refers to a Disk-Equatorial. I call it the Cylinder and Band versions Equatorials because they measure time in the same direct way that a Disk-Equatorial does. ...but their dial-surface is parallel to the Earth's polar-axis so someone could argue that they should be called Polar Band or Cylinder dials. So what are they correctly called? Michael Ossipoff .. On Wed, Oct 18, 2017 at 3:29 AM, Nathaniel Shippen wrote: > Well, my first attempt at a sundial is about the simplest you could > imagine. However, I did follow Albert Waugh's suggestion in "Sundials: > Their Theory And Construction" and offset the time marks to Hawaii Standard > Time, so I only have to keep the daily Equation of Time value in mind. Note > that the 12:30 mark is almost vertically below the gnomon. At my location > near Honolulu mean solar time is 32 minutes behind HST (GMT - 10). In fact > until after World War 2 clocks in Hawaii were set to GMT - 10:30, much > closer to mean solar time throughout the state. In 1947 Hawaii was > shoehorned into the GMT - 10 timezone also used in the Aleutian Islands. > > https://en.wikipedia.org/wiki/Hawaii%E2%80%93Aleutian_Time_Zone > > Nathaniel Shippen > > On Wed, Oct 18, 2017 at 3:53 AM, Michael Ossipoff > wrote: > >> But, if you're willing to give up the Horizontal-Dial's advantages, then >> an Equatorial-Dial has the following advantages: >> >> 1. Its equally-spaced hour-lines allow perfectly accurate linear >> interpolation of the time, when the shadow is between hour-lines. >> >> (But, when usiing pocket horizontal tablet-dials, linear interpolation >> gave results accurate with 3 minutes, when only the hours and half-hours >> were marked. So interpolation with unequally-spaced hour-lines doesn't seem >> a problem.) >> >> 2. Its principle is obvious. The Horizontal-Dial's construction-principle >> isn't difficult to explain, but the Equatorial's construction-principle is >> obvious at a glance. It would make perfect sense to anyone, without any >> explanation. >> >> (By the way, it's true that a Bifilar Dial shares the advantage of >> equally-spaced hour-lines. But it only tells time for part of the day, >> because, when the Sun is low, the shadow of interest won't be on the >> dial-plate.) >> >> Of course a two-sided Disk-Equatorial is incomparably easier to construct >> than a Band-Equatorial or Cylinder-Equatorial. ...if you don't mind the >> fact that a Disk-Equatorial can only be read from the north in the summer, >> and from the south in the winter. >> >> Michael Ossipoff >> >> >> >> >> On Mon, Oct 16, 2017 at 8:48 AM, Brad Thayer > > wrote: >> >>> I am looking to make a hemicyclium-type sundial (half-hemisphere) in a >>> metal working class. What little I can find on them says they are >>> inaccurate, without being very clear on the problem. It appears to me the >>> only issue is it needs to be tilted so that the gnomon aligns with the >>> Earth’s rotation axis; thus the half-bowl faces south and the gnomon points >>> south, but the end of the gnomon that attaches to the bowl points north. >>> Am I missing anything? I am also looking to use an analemma-shaped gnomon >>> to cast the shadow on the bowl, and at least month lines for
Re: Hemicyclium correction
Brad-- > > If the inside surface is marked with the lines analogous to lines of > longitude on a globe spaced 15 degrees apart, radiating from the “pole” of > the hemicyclium, and the entire device is tilted to align with the earth’s > axis, would it then read out in Local True Solar Time? > Yes, the hour-lines would be exactly like the 15-degree meridian longitude-lines of a globe. (plus whatever intermediate fractional-hour lines). It seems to me that, in the photos and drawings I've seen, both the Hemicyclia and the Hemispheria had a horizontal flat top edge-surface. With that bowl-edge horizontal, and with the stick-tip nodus at the same level as that bowl-edge, the dial wIould tell time whenever the Sun is above the horizon. (So do the Horizontal Dial, the Band-Equatorial, and lots of others) It also seems to me that, in the photos and drawings that I've seen, the stick for the stick-end nodus was horizontal, sticking out so that its tip, the nodus, is at the center of the bowl. If you're sure you want the bigger task of a Hemicyclium instead of a Band-Equatorial, then I'd use the traditional horizontal stick, with its end (nodus) at the bowl's center. ...instead of using a polar-parallel gnomon. Easier, for one thing, and more realistic, for a Hemicyclium or Hemispherium. Though the system of hour-lines should have its poles at the ends of an imaginary line parallel with the Earth's axis (north-south, tipped up at the north-end by an amount equal to your north-latitude), I'd just leave the top-cut, bowl-edge horizontal, like the pictures that i've seen. Anyway, if the surface that includes the bowl edge were tipped from the horizontal, wouldn't that interfere with ensuring that the dial will tell time whenever the Sun is above the horizon? I'd leave the bowl-top edge horizontal. I think that's how Hemicyclia and Hemispheria always were. I'd have declination-lines in the bowl, in addition to the hour-lines. Of course the declination-lines would be exactly like the parallels on a globe. People often mark declination-lines with the date. I'd have the lines marked with declination-degrees as well. In older centuries, they marked declination-lines with zodiac signs instead of month-names. That made sense really, because the zodiac signs coincide with exact solar ecliptic longitudes, corresponding to exact declinations (if you disregard the small change-rate of the obliquity). But of course nowadays the months are much more famiiar. But I'd mark the declination-lines in degrees too. That is my primary sticking point. I’d prefer that than the ancient Temporary hours. It would seem it would be mathematically similar to a section of an armillary sphere. Yes, just maybe a more challenging construction than an Armillary Band-Equatorial. The globe-meridian-like hour-lines would be more work than the straight hour lines on a Band-Equatorial. But, with your metal-working experience, you probably *want* something more challenging. > > > With a proper adjustable mount, I can adjust for the longitude correction > (I am currently about 4 degrees away from my nearest meridian) and DST > twice a year as well. > Ok, but that seems unnecessary extra work, since the longitude-correction could be added to EoT in your conversion-table plaque displayed near the dial. Anyway, it seems more aesthetic for a dial to give Local True Solar Time. Interesting project. I once considered proposing a project of a brass band-equatorial mounted in a concrete structure resembling a Hemicyclium. The copper bowl will have a cool ancient look when it weathers. Michael Ossipoff > > *From:* Michael Ossipoff [mailto:email9648...@gmail.com] > *Sent:* Tuesday, October 17, 2017 8:44 PM > *To:* Brad Thayer > *Cc:* sundial list > *Subject:* Re: Hemicyclium correction > > > > > > > > On Mon, Oct 16, 2017 at 8:48 AM, Brad Thayer > wrote: > > I am looking to make a hemicyclium-type sundial (half-hemisphere) in a > metal working class. What little I can find on them says they are > inaccurate, without being very clear on the problem. > > > > But the way, I've seen it spelled "Hemicycleum" as well. I don't know > which is correct, but "Hemicycleum" looks better, it seems to me. But I'll > use your spelling. It's probably better-accpeted. > > > > Whoever said that was mistaken. Hemicyclia are as in principle as accurate > as any sundial can be. > > > > In ancient times, Hemicyclia were devised, instead of our modern > polar-gnomon garden sundial, or our equatorial sundials, because in those > days, they weren't using our Equal-Hours for civil time (Astronomers used > it though). They were using "Temporary Hours), that divided each day into > 12 equal hours, fo
Re: Hemicyclium correction
Just one safety quibble: If you mount the spike sticking up, then it will be an eye-hazard, even with the ball on its end. That's a good reason to mount the spike horizontally, at the rim of the bowl. It could be mounted in a north-south groove at the south side of the bowl. Mounting the spike at the south side of the bowl is likewise probably best for eye-safety, because people will more likely be reading the dial from its south side. ...because the dial-lines are mostly toward the north side. That's probably traditional too. Anyway, that's traditional, it seems to me, and so it's better of ancient realism. Besides, with the spike horizontal, its tip-nodus will still have a shadow that the spike itself doesn't get in the way of at equinox noon. Michael Ossipoff f . On Thu, Oct 19, 2017 at 11:13 AM, Frank King wrote: > Dear Brad, > > I'm delighted that you enjoyued > my "tutorial"... > > > However, its your step 19 I am > > interested in. > > Ah yes. That's where I mention > marking out equal hours. I thought > you would be most interested in > that step :-) > > You add... > > > And if I do tilt the hemispherium > > so that the horizon line is now > > instead parallel to the earth's > > axis, does that solve any of the > > issues? > > This is like taking an aircraft as > your inspiration for designing a > car and not appreciating what the > wings are for. > > The absolutely key feature of the > hemicyclium design is that, at its > top, there is a FLAT HORIZONTAL > surface. > > It isn't like that just so the > Greek user could put his Retsina > glass on it. It is like that in > order to be parallel to the plane > of the horizon and... > > That is important because it > echos the position of the sun at > sunrise and sunset and... > > That is important because the > principal purpose of this dial > was to divide the day into > equal intervals of time starting > at sunrise and ending at sunset. > > These unequal hours may not be > to your taste but this is the > scheme that was in widespread > use for thousands of years! > Why not educate your friends? > Why not educate yourself? > > OK, I'll get round to what you > really want shortly but, meantime, > I am going to stick to the original > purpose... > > In my previous message I was > simplifying matters by saying > that you should cut the sphere > (the orange) into quarters. > > The problem with using a quarter > of a sphere (and this also applies > if you insist on equal hours) is > that you can't represent sunrise > and sunset in the summer months. > > A real hemicyclium was rather more > than a quarter of a sphere. Take > a look at: > > http://www.sundials.co.uk/leicester/fig04.jpg > > You can see the horizontal surface > easily enough and you can also see > a forward-sloping face at the front. > > The slope, relative to the vertical, > matches the local latitude. This is > about 37 degrees off the vertical > in Greece but 50+ in the U.K. > > By leaning forward this allows the > horizontal surface to grow so that > its inside rim is no longer a > semi-circle. It is now much more > of a circle. The tip of the spike > serves as the nodus and this is at > the centre of the rim circle. The > two "wings" are way beyond this > tip. > > If you look at the markings you can see > the three main constant-declination > arcs. The middle one is a great circle > and the tip of the spike is the centre > of this circle too. > > The upper arc is for the winter > solstice and the lower is for the > summer solstice. These are small > circles. If you hold one end of > a piece of string on the tip of > the spike and run the other end > round either of these circles > you would see the string sweeps > out a cone, not a disc. > > OK, once you have this elegant > hollow shape you can make cardboard > templates which exactly fit these > three circular arcs. The template > for the equinoctial arc will be an > exact semi-circle. The other two > have a slightly smaller radius > than the equinoctial circle. > > Clearly, the template for the > summer solstice is more than a > semi-circle and that for the > winter solstice is less than > a semi-circle. If you fit the > two together you should get a > perfect circle. Can you see > why? > > Now all you have to do is to > divide the rims of each of these > three circles into 12 equal parts. > This gives you the unequal hours > of the day exactly as in fig 4. > > Of course, what you really want > are new-fangle
Re: Hemicyclium correction
Brad-- I don't know if this is of interest or not, because I realize that the Hemicyclium is your main project. If you have any of that 6-inch diameter copper tubing left, then why not cut off a section of it, with width equal to half the diameter, for an additional project that can be completed much more quickly, giving you an interesting and accurate south-window-sill dial, while you're working on the main project, the Hemicyclium. This would be a Cylinder-Equatorial Dial, with a circumference-aperature nodus, to cast a light-spot on the inside surface of the cylinder. Such a dial is most easily read from the north, from above the dial. In other words, it would be perfect for a window-sill dial, for a south window For a south windowsill, that kind of dial has major advantages. Unlike a horizontal dial on a south windowsill, it doesn't have a gnomon that's pointing up toward the observer (eye-hazard) Being an Equatorial, its hour-lines are equally-spaced, for the easiest accurate linear-interpolation of the time between hour-lines. (Of course the Hemicyclium, being effectively an Equatorial Dial too, shares that advantage.) And because, over a 12-hour period, the light-spot travels the entire circumference of the cylinder, the lines for the hours will be over an inch and a half apart. ...making it that much easier to read the time. ...especially since that great amount of space between hour-lines allows the convenient reading of quarter hour (or maybe 10-minute) lines. You'd drill the circumference-aperature at the middle of the cylinder's width. If the width is half of the diameter (.4335 times the diameter would be enough), then there will be room for the circumferance-aperature's light-spot to be on the cylinder all year. A disadvantage is that this type of dial only tells 12 hours of time. But as I mentioned in an earlier post, that can be remedied by having more than one circumferance-aperature nodus. Of course if your house faces due south, then a south-windowsill dial won't have more than 12 hours of sunlight anyway. But suppose that your house is facing a little left or right of due south. Then you'll be getting some sunlight before 6:00 a.m. or after 6:00 p.m. Say, for example that your house faces a little left of due south. Then you get a little bit of sun on the windowsill before 6:00 a.m. So drill a circumference aperature at the 6:00 p.m. line, at the left (east) side of the cylinder. Of course you'd have to be sure tor read the right light-spot. You could have special early-morning time markings on the cylinder for early mornings. Of course it would be the reverse if your house faces a little to the right of due south. Of course you could cover the early-morning circumference aperature when it isn't in use. A Cylinder-Equatorial is a good choice for a south windowsill, and, if you have any of that 6-inch tubing left over, then it would be a quick project, and you'd have a windowsill dial while working on your main project, the Hemicyclium. Michael Ossipoff On Wed, Oct 18, 2017 at 10:23 PM, Brad Thayer wrote: > Michael, > > > > Thank you for the lengthy response. > > > > This will actually be the fifth sundial I have completed (and the 6th > that I have started). I’ve already made a band-equatorial (using “Mayan > digits”), two analemmatic horizonatal sundials, a south-facing vertical > sundial, and started a cylindrical sundial (aka, shepherds staff). With > each one, I try something new and challenging. I also use it as a way to > improve my metal working skills. As I am currently taking a copper > raising/sinking and chasing metal forming class, I was interested in making > a bowl with chased lines (aka, repousse) for practice, hence the idea for > the hemicyclium. > > > > I lucked into some used 14 gauge copper tubing about 6 inches in diameter, > which I annealed, cut open and pounded flat as a starting point. So I have > the basic starting materials. > > > > If the inside surface is marked with the lines analogous to lines of > longitude on a globe spaced 15 degrees apart, radiating from the “pole” of > the hemicyclium, and the entire device is tilted to align with the earth’s > axis, would it then read out in Local True Solar Time? That is my primary > sticking point. I’d prefer that than the ancient Temporary hours. It > would seem it would be mathematically similar to a section of an armillary > sphere. > > > > With a proper adjustable mount, I can adjust for the longitude correction > (I am currently about 4 degrees away from my nearest meridian) and DST > twice a year as well. > > > > *From:* Michael Ossipoff [mailto:email9648...@gmail.com] > *Sent:* Tuesday, October 17, 2017 8:44 PM > *To:* Brad Thayer > *Cc:* sundial list > *Subject:*
Re: Hemicyclium correction
Of course, for the Cylinder Equatorial with circumference aperature, you could have declination-ilnes, which would be circles around the cylinder's circumference. Michael Ossipoff On Wed, Oct 18, 2017 at 10:23 PM, Brad Thayer wrote: > Michael, > > > > Thank you for the lengthy response. > > > > This will actually be the fifth sundial I have completed (and the 6th > that I have started). I’ve already made a band-equatorial (using “Mayan > digits”), two analemmatic horizonatal sundials, a south-facing vertical > sundial, and started a cylindrical sundial (aka, shepherds staff). With > each one, I try something new and challenging. I also use it as a way to > improve my metal working skills. As I am currently taking a copper > raising/sinking and chasing metal forming class, I was interested in making > a bowl with chased lines (aka, repousse) for practice, hence the idea for > the hemicyclium. > > > > I lucked into some used 14 gauge copper tubing about 6 inches in diameter, > which I annealed, cut open and pounded flat as a starting point. So I have > the basic starting materials. > > > > If the inside surface is marked with the lines analogous to lines of > longitude on a globe spaced 15 degrees apart, radiating from the “pole” of > the hemicyclium, and the entire device is tilted to align with the earth’s > axis, would it then read out in Local True Solar Time? That is my primary > sticking point. I’d prefer that than the ancient Temporary hours. It > would seem it would be mathematically similar to a section of an armillary > sphere. > > > > With a proper adjustable mount, I can adjust for the longitude correction > (I am currently about 4 degrees away from my nearest meridian) and DST > twice a year as well. > > > > *From:* Michael Ossipoff [mailto:email9648...@gmail.com] > *Sent:* Tuesday, October 17, 2017 8:44 PM > *To:* Brad Thayer > *Cc:* sundial list > *Subject:* Re: Hemicyclium correction > > > > > > > > On Mon, Oct 16, 2017 at 8:48 AM, Brad Thayer > wrote: > > I am looking to make a hemicyclium-type sundial (half-hemisphere) in a > metal working class. What little I can find on them says they are > inaccurate, without being very clear on the problem. > > > > But the way, I've seen it spelled "Hemicycleum" as well. I don't know > which is correct, but "Hemicycleum" looks better, it seems to me. But I'll > use your spelling. It's probably better-accpeted. > > > > Whoever said that was mistaken. Hemicyclia are as in principle as accurate > as any sundial can be. > > > > In ancient times, Hemicyclia were devised, instead of our modern > polar-gnomon garden sundial, or our equatorial sundials, because in those > days, they weren't using our Equal-Hours for civil time (Astronomers used > it though). They were using "Temporary Hours), that divided each day into > 12 equal hours, for their civil time. > > > > To achieve that, they used a stick-tip nodus or bead-nodus. to cast a > point-shadow on the hemicyclium surface. As the Sun's declination changes > seasonally, of course the tip-nodus's path on the hemicyclium changes too. > So the hour-lines were curves, drawn so that, for any particular solar > declination, those marks divide the day (sunrise to sunset) into 12 equal > parts. > > > > As you can imagine, that makes the dial more complicated than modern ones. > "Early" doesn't always mean "simpler". > > > > ...and so there was much opportunity for error in the calclulations and > drafting,for those curved hour-lines. > > > > So maybe some hemicyclia *were* inaccurately drafted. For one thing, of > course the exact time of day wasn't as crucial in those days, and of course > the more precisely made, and prestigiously made, a sundial was, the more it > was likely to cost. > > > > But there's no reason why your hemicyclium should be made for Temporary > Hours. Make it for our modern Equal-Hours, also referred to as Local True > Solar Time (LTST). > > > > > > It appears to me the only issue is it needs to be tilted so that the > gnomon aligns with the Earth’s rotation axis; > > > > The equinox circle on the Hemicyclium, the line that the tip-nodus follows > on the day of the equinox, should be a circle parallel to the celestial > equator. > > > > And yes, if you're going to use a polar gnomon instead of a tip-nodus, > then that polar gnomon should be parallel to the Earth's axis, pointed at > the north celestial pole. ...and should go through the center of the sphere > from which the Hemicy
Re: Hemicyclium correction
Correction: I said that the declination lines would be circles around the cylinder's inside circumference. Actually, because the distance of the light-spot from the circumference-aperature varies, around the dial, the declination lines wouldn't be that simple. The drawing of the declination lines would just be a bit trickier. At a certain hour-line, the axial displacement of the declination-line from the equinox line would be equal to the tangent of the declination, times the straight-line distance between the circumference aperature and the place where the hour-line intersects the equinox line. If a cone (such as a drinking-cup) is used instead of a cylinder, that complicates the declination-lines a bit more, but it's still do-able. I've read that, in ancient times, drinking-cups, perforated with a circumference-aperature nodus, were sometimes used as portable sundials. Presumably, for some particular property-area, a person might know what tree, building or mountain landmark was due north. S/he could point the cup in that direction, with the circumference aperature on top, pointing the cup upward so that its axis points above the horizontal by an amount approximately equal to the local latitude. ...and read the time from the hour-lines marked inside the cup. Obviously the circumference-aperature would limit how high you could fill the cup, when using it for drinking. Michael Ossipoff On Thu, Oct 19, 2017 at 2:31 PM, Michael Ossipoff wrote: > Of course, for the Cylinder Equatorial with circumference aperature, you > could have declination-ilnes, which would be circles around the cylinder's > circumference. > > Michael Ossipoff > > On Wed, Oct 18, 2017 at 10:23 PM, Brad Thayer > wrote: > >> Michael, >> >> >> >> Thank you for the lengthy response. >> >> >> >> This will actually be the fifth sundial I have completed (and the 6th >> that I have started). I’ve already made a band-equatorial (using “Mayan >> digits”), two analemmatic horizonatal sundials, a south-facing vertical >> sundial, and started a cylindrical sundial (aka, shepherds staff). With >> each one, I try something new and challenging. I also use it as a way to >> improve my metal working skills. As I am currently taking a copper >> raising/sinking and chasing metal forming class, I was interested in making >> a bowl with chased lines (aka, repousse) for practice, hence the idea for >> the hemicyclium. >> >> >> >> I lucked into some used 14 gauge copper tubing about 6 inches in >> diameter, which I annealed, cut open and pounded flat as a starting point. >> So I have the basic starting materials. >> >> >> >> If the inside surface is marked with the lines analogous to lines of >> longitude on a globe spaced 15 degrees apart, radiating from the “pole” of >> the hemicyclium, and the entire device is tilted to align with the earth’s >> axis, would it then read out in Local True Solar Time? That is my primary >> sticking point. I’d prefer that than the ancient Temporary hours. It >> would seem it would be mathematically similar to a section of an armillary >> sphere. >> >> >> >> With a proper adjustable mount, I can adjust for the longitude correction >> (I am currently about 4 degrees away from my nearest meridian) and DST >> twice a year as well. >> >> >> >> *From:* Michael Ossipoff [mailto:email9648...@gmail.com] >> *Sent:* Tuesday, October 17, 2017 8:44 PM >> *To:* Brad Thayer >> *Cc:* sundial list >> *Subject:* Re: Hemicyclium correction >> >> >> >> >> >> >> >> On Mon, Oct 16, 2017 at 8:48 AM, Brad Thayer >> wrote: >> >> I am looking to make a hemicyclium-type sundial (half-hemisphere) in a >> metal working class. What little I can find on them says they are >> inaccurate, without being very clear on the problem. >> >> >> >> But the way, I've seen it spelled "Hemicycleum" as well. I don't know >> which is correct, but "Hemicycleum" looks better, it seems to me. But I'll >> use your spelling. It's probably better-accpeted. >> >> >> >> Whoever said that was mistaken. Hemicyclia are as in principle as >> accurate as any sundial can be. >> >> >> >> In ancient times, Hemicyclia were devised, instead of our modern >> polar-gnomon garden sundial, or our equatorial sundials, because in those >> days, they weren't using our Equal-Hours for civil time (Astronomers used >> it though). They were using "Temporary Hours), that divided each day into >> 12 equal hours,
Re: Hemicyclium correction
In the Hemicyclium discussion, the OP mentioned having 6-inch copper tubing. So, though it was a bit off-topic, I suggested that the tubing could be used for an additional, quicker, project, to make a south windowsill sundial--a Circumference-Aprerture Cylindrical Equatorial Dial. But, when I said that the axial dimension of the cylinder has to be at least 0.4335 times the diameter, I neglected the fact that there are south declinations as well as north declinations. (...funny, because we're in south declination now) So, with the circumference aperture in the middle of the cylinder, the cylinder's axial dimension has to be at least twice 0.4335, which is about 0.867 times the diameter. But my suggestion for marking points of the declination-lines for each hour was correct: At any hour-line, the axial displacement of a declination-line from the equinox-line is equal to the tangent of the declination times the direct distance between the circumference aperture and the intersection of that hour-line with the equinox-line That amounts to: (Tan dec)(R*2Sin(h) ). ...where h is the number hours from 12 noon.where R is the cylinderr's radius. Obviously more neatly written: (Tan dec)(DSin(h) ). ...where D is the diameter of the cylinder. - But a cone would be better than a cylinder, because it opens toward the north, the direction from which it would be observed--making it readable from a wider-range of directions, and making the inside surface more readable in generral. The use of a cone just slightly more complicates the declination-lines, but that would take this post even more off-topic. -- I mentioned that I'd read of a drinking-cup with a hole in it being used as a cylindrical sundial. Of course if it were a Cylindrical Equatorial, orienting it just by estimation wouldn't give very accurate results. (A Cylindrical Equatorial is supposed to be a *mounted* dial, not a portable dial). But actually, maybe they were talking about a Cylindrical *Altitude* Dial. But, though that avoids the direction-estimation, the drinking-cup would need a way of hanging it in the right orientation, and so it wouldn't be much like an ordinary drinking-cup. ...and the line-marking would be complicated by the non-cylindrical shape of the cup. Michael Ossipoff On Mon, Oct 16, 2017 at 8:48 AM, Brad Thayer wrote: > I am looking to make a hemicyclium-type sundial (half-hemisphere) in a > metal working class. What little I can find on them says they are > inaccurate, without being very clear on the problem. It appears to me the > only issue is it needs to be tilted so that the gnomon aligns with the > Earth’s rotation axis; thus the half-bowl faces south and the gnomon points > south, but the end of the gnomon that attaches to the bowl points north. > Am I missing anything? I am also looking to use an analemma-shaped gnomon > to cast the shadow on the bowl, and at least month lines for the solar > elevation. The bowl will also have a rod and bracket on the bottom to > allow it to be rotated for daylight-savings time and for local longitude > corrections. > > > > Thanks in advance -- Brad > > --- > https://lists.uni-koeln.de/mailman/listinfo/sundial > > > --- https://lists.uni-koeln.de/mailman/listinfo/sundial
Re: Hemicyclium correction - a figure might be needed
Hi-- I'll look for some images of Circumference-Aperture Cylinder-Equatorials.and Cone-Equatorials. It can be shown that the light-spot projected by the circumference-aperture moves around the inside of the cylinder at a uniform rate that's twice the rate at which an axial-gnomon's shadow would move. So, during the 12 hours from 6:00 a.m. to 6:00 p.m, the light-spot moves all the way around the inside of the cylinder, while the shadow of an axial gnomon would only move halfway around the cylinder. (But, as I was saying, if the south-window isn't facing due-south, and so the early sunrise or late sunset illuminates the dial, then an additional circumference aperture could be added at the 6:00 p.m. line, on the east side of the cylinder, or at the 6:00 a.m. line, on the west side of the cylinder. In that way, the dial would have more than 12-hour coverage.) So, with the hour-lines twice as far apart, the dial is that much easier to read accurately. The spacing between hour-lines is .2618 times the diameter of the cylinder. - Of course, with a Cylinder-Equatorial dial, with the circumference-aperture at the middle of the cylinder, with the declination-line-area having an axial dimension of 0.867*D, the mid-summer position of the light-spot will be far down the cylinder, where it could be more difficult to read. That could be a reason to prefer a Cone-Equatorial. But, with a Cylinder-Equatorial, the situation could be remedied by adding another circumference-aperture barely south of the top of the north edge of the cylinder. ...or a notch in the north edge of the cylinder. So, in north declination, the south-notch would be used. And in north declination, the circumference-aperture would be used. But then you'd need two separate sets of declination-lines, one for north declination, and another for south declination. Maybe one set of lines could be dotted. Or maybe one set of declination-lines, labeled on the east side of the cylinder could be solid lines on that side, and dotted on the other side. And likewise for the other set of declination-lines, labeled on the west side, solid on that side and dotted on the other side. -- Of course, instead of a circumference-aperture and an edge-notch, one could instead use two edge-notches, one north and one south. But then the cylinder would best be cut to an axial-dimension of 0.867*D. That would increase the work of making the dial, and the force involved in sawing or cutting could deform the cylinder.. The appeal of the combination of a circumference-aperature in the top- middle, and an edge-notch at the top of the north-edge (or just using the aperture and no notch), is that the cylinder wouldn't have to be sawed or cut. With the cylinder or cone supported at its north end by a support with a semicircular hole in which the north end of the cylinder rests, and with the south-end of the cylinder resting on the window-sill, of course the cylinder's inclination above the horizontal is easily adjusted by sliding the cylinder (or cone) northward or southward ...to incline the cylinder or cone with its axis parallel to the Earth's axis. Michael Ossipoff On Tue, Oct 24, 2017 at 4:33 AM, wrote: > Thank you for your nice considerations. > > I think that some kind of visualization would make them more clear to a > general public. Could you please support your ideas with a figure or a link > to an external one (if exists)? > > > > Best regards, > > Wojtek > > > > *From: *Michael Ossipoff > *Sent: *Tuesday, October 24, 2017 1:32 AM > *To: *Brad Thayer > *Cc: *sundial list > *Subject: *Re: Hemicyclium correction > > > > > > In the Hemicyclium discussion, the OP mentioned having 6-inch copper > tubing. So, though it was a bit off-topic, I suggested that the tubing > could be used for an additional, quicker, project, to make a south > windowsill sundial--a Circumference-Aprerture Cylindrical Equatorial Dial. > > But, when I said that the axial dimension of the cylinder has to be at > least 0.4335 times the diameter, I neglected the fact that there are south > declinations as well as north declinations. (...funny, because we're in > south declination now) So, with the circumference aperture in the middle of > the cylinder, the cylinder's axial dimension has to be at least twice > 0.4335, which is about 0.867 times the diameter. > > But my suggestion for marking points of the declination-lines for each > hour was correct: > > At any hour-line, the axial displacement of a declination-line from the > equinox-line is equal to the tangent of the declination times the direct > distance between the circumference aperture and the intersection of that > hour-line with the equinox-line > > That
Re: Hemicyclium correction - a figure might be needed
Typo: When I said: "So, in north declination, the south-notch would be used." ...I meant "*north*-notch". Michael Ossipoff On Tue, Oct 24, 2017 at 4:33 AM, wrote: > Thank you for your nice considerations. > > I think that some kind of visualization would make them more clear to a > general public. Could you please support your ideas with a figure or a link > to an external one (if exists)? > > > > Best regards, > > Wojtek > > > > *From: *Michael Ossipoff > *Sent: *Tuesday, October 24, 2017 1:32 AM > *To: *Brad Thayer > *Cc: *sundial list > *Subject: *Re: Hemicyclium correction > > > > > > In the Hemicyclium discussion, the OP mentioned having 6-inch copper > tubing. So, though it was a bit off-topic, I suggested that the tubing > could be used for an additional, quicker, project, to make a south > windowsill sundial--a Circumference-Aprerture Cylindrical Equatorial Dial. > > But, when I said that the axial dimension of the cylinder has to be at > least 0.4335 times the diameter, I neglected the fact that there are south > declinations as well as north declinations. (...funny, because we're in > south declination now) So, with the circumference aperture in the middle of > the cylinder, the cylinder's axial dimension has to be at least twice > 0.4335, which is about 0.867 times the diameter. > > But my suggestion for marking points of the declination-lines for each > hour was correct: > > At any hour-line, the axial displacement of a declination-line from the > equinox-line is equal to the tangent of the declination times the direct > distance between the circumference aperture and the intersection of that > hour-line with the equinox-line > > That amounts to: > > > > (Tan dec)(R*2Sin(h) ). > > ...where h is the number hours from 12 noon.where R is the cylinderr's > radius. > > Obviously more neatly written: > > > (Tan dec)(DSin(h) ). > > ...where D is the diameter of the cylinder. > > - > > > > But a cone would be better than a cylinder, because it opens toward the > north, the direction from which it would be observed--making it readable > from a wider-range of directions, and making the inside surface more > readable in generral. The use of a cone just slightly more complicates the > declination-lines, but that would take this post even more off-topic. > > -- > > I mentioned that I'd read of a drinking-cup with a hole in it being used > as a cylindrical sundial. Of course if it were a Cylindrical Equatorial, > orienting it just by estimation wouldn't give very accurate results. (A > Cylindrical Equatorial is supposed to be a *mounted* dial, not a portable > dial). > > But actually, maybe they were talking about a Cylindrical *Altitude* > Dial. But, though that avoids the direction-estimation, the drinking-cup > would need a way of hanging it in the right orientation, and so it wouldn't > be much like an ordinary drinking-cup. ...and the line-marking would be > complicated by the non-cylindrical shape of the cup. > > > > Michael Ossipoff > > > > On Mon, Oct 16, 2017 at 8:48 AM, Brad Thayer > wrote: > > I am looking to make a hemicyclium-type sundial (half-hemisphere) in a > metal working class. What little I can find on them says they are > inaccurate, without being very clear on the problem. It appears to me the > only issue is it needs to be tilted so that the gnomon aligns with the > Earth’s rotation axis; thus the half-bowl faces south and the gnomon points > south, but the end of the gnomon that attaches to the bowl points north. > Am I missing anything? I am also looking to use an analemma-shaped gnomon > to cast the shadow on the bowl, and at least month lines for the solar > elevation. The bowl will also have a rod and bracket on the bottom to > allow it to be rotated for daylight-savings time and for local longitude > corrections. > > > > Thanks in advance -- Brad > > > --- > https://lists.uni-koeln.de/mailman/listinfo/sundial > > > > > > --- > https://lists.uni-koeln.de/mailman/listinfo/sundial > > > --- https://lists.uni-koeln.de/mailman/listinfo/sundial
Re: Hemicyclium correction - a figure might be needed
Another typo: When I said: "And in north declination, the circumference-aperture would be used." I mean that in *south* declination the circumference-aperature would be used. Michael Ossipoff On Tue, Oct 24, 2017 at 4:33 AM, wrote: > Thank you for your nice considerations. > > I think that some kind of visualization would make them more clear to a > general public. Could you please support your ideas with a figure or a link > to an external one (if exists)? > > > > Best regards, > > Wojtek > > > > *From: *Michael Ossipoff > *Sent: *Tuesday, October 24, 2017 1:32 AM > *To: *Brad Thayer > *Cc: *sundial list > *Subject: *Re: Hemicyclium correction > > > > > > In the Hemicyclium discussion, the OP mentioned having 6-inch copper > tubing. So, though it was a bit off-topic, I suggested that the tubing > could be used for an additional, quicker, project, to make a south > windowsill sundial--a Circumference-Aprerture Cylindrical Equatorial Dial. > > But, when I said that the axial dimension of the cylinder has to be at > least 0.4335 times the diameter, I neglected the fact that there are south > declinations as well as north declinations. (...funny, because we're in > south declination now) So, with the circumference aperture in the middle of > the cylinder, the cylinder's axial dimension has to be at least twice > 0.4335, which is about 0.867 times the diameter. > > But my suggestion for marking points of the declination-lines for each > hour was correct: > > At any hour-line, the axial displacement of a declination-line from the > equinox-line is equal to the tangent of the declination times the direct > distance between the circumference aperture and the intersection of that > hour-line with the equinox-line > > That amounts to: > > > > (Tan dec)(R*2Sin(h) ). > > ...where h is the number hours from 12 noon.where R is the cylinderr's > radius. > > Obviously more neatly written: > > > (Tan dec)(DSin(h) ). > > ...where D is the diameter of the cylinder. > > - > > > > But a cone would be better than a cylinder, because it opens toward the > north, the direction from which it would be observed--making it readable > from a wider-range of directions, and making the inside surface more > readable in generral. The use of a cone just slightly more complicates the > declination-lines, but that would take this post even more off-topic. > > -- > > I mentioned that I'd read of a drinking-cup with a hole in it being used > as a cylindrical sundial. Of course if it were a Cylindrical Equatorial, > orienting it just by estimation wouldn't give very accurate results. (A > Cylindrical Equatorial is supposed to be a *mounted* dial, not a portable > dial). > > But actually, maybe they were talking about a Cylindrical *Altitude* > Dial. But, though that avoids the direction-estimation, the drinking-cup > would need a way of hanging it in the right orientation, and so it wouldn't > be much like an ordinary drinking-cup. ...and the line-marking would be > complicated by the non-cylindrical shape of the cup. > > > > Michael Ossipoff > > > > On Mon, Oct 16, 2017 at 8:48 AM, Brad Thayer > wrote: > > I am looking to make a hemicyclium-type sundial (half-hemisphere) in a > metal working class. What little I can find on them says they are > inaccurate, without being very clear on the problem. It appears to me the > only issue is it needs to be tilted so that the gnomon aligns with the > Earth’s rotation axis; thus the half-bowl faces south and the gnomon points > south, but the end of the gnomon that attaches to the bowl points north. > Am I missing anything? I am also looking to use an analemma-shaped gnomon > to cast the shadow on the bowl, and at least month lines for the solar > elevation. The bowl will also have a rod and bracket on the bottom to > allow it to be rotated for daylight-savings time and for local longitude > corrections. > > > > Thanks in advance -- Brad > > > --- > https://lists.uni-koeln.de/mailman/listinfo/sundial > > > > > > --- > https://lists.uni-koeln.de/mailman/listinfo/sundial > > > --- https://lists.uni-koeln.de/mailman/listinfo/sundial
Re: Hemicyclium correction
Correction: I'd said: (Tan dec)(R*2Sin(h) ). ...where h is the number hours from 12 noon.where R is the cylinder's radius. Here's the correction: Instead of "hours from 12 noon", It should say: "...where h is 15 degrees times the number of hours from 6 a.m., during the a.m. hours, or the number of hours from 6 p.m., during the p.m. hours." ...which could also be said as: " 15 degrees times (6 minus the number of hours from 12 noon)". ...for the hours from 6 a.m. to 6 p.m. Michael Ossipoff On Mon, Oct 23, 2017 at 7:31 PM, Michael Ossipoff wrote: > > In the Hemicyclium discussion, the OP mentioned having 6-inch copper > tubing. So, though it was a bit off-topic, I suggested that the tubing > could be used for an additional, quicker, project, to make a south > windowsill sundial--a Circumference-Aprerture Cylindrical Equatorial Dial. > > But, when I said that the axial dimension of the cylinder has to be at > least 0.4335 times the diameter, I neglected the fact that there are south > declinations as well as north declinations. (...funny, because we're in > south declination now) So, with the circumference aperture in the middle of > the cylinder, the cylinder's axial dimension has to be at least twice > 0.4335, which is about 0.867 times the diameter. > > But my suggestion for marking points of the declination-lines for each > hour was correct: > > At any hour-line, the axial displacement of a declination-line from the > equinox-line is equal to the tangent of the declination times the direct > distance between the circumference aperture and the intersection of that > hour-line with the equinox-line > > That amounts to: > > (Tan dec)(R*2Sin(h) ). > > ...where h is the number hours from 12 noon.where R is the cylinderr's > radius. > > Obviously more neatly written: > > (Tan dec)(DSin(h) ). > > ...where D is the diameter of the cylinder. > - > > But a cone would be better than a cylinder, because it opens toward the > north, the direction from which it would be observed--making it readable > from a wider-range of directions, and making the inside surface more > readable in generral. The use of a cone just slightly more complicates the > declination-lines, but that would take this post even more off-topic. > -- > > I mentioned that I'd read of a drinking-cup with a hole in it being used > as a cylindrical sundial. Of course if it were a Cylindrical Equatorial, > orienting it just by estimation wouldn't give very accurate results. (A > Cylindrical Equatorial is supposed to be a *mounted* dial, not a portable > dial). > > But actually, maybe they were talking about a Cylindrical *Altitude* > Dial. But, though that avoids the direction-estimation, the drinking-cup > would need a way of hanging it in the right orientation, and so it wouldn't > be much like an ordinary drinking-cup. ...and the line-marking would be > complicated by the non-cylindrical shape of the cup. > > Michael Ossipoff > > On Mon, Oct 16, 2017 at 8:48 AM, Brad Thayer > wrote: > >> I am looking to make a hemicyclium-type sundial (half-hemisphere) in a >> metal working class. What little I can find on them says they are >> inaccurate, without being very clear on the problem. It appears to me the >> only issue is it needs to be tilted so that the gnomon aligns with the >> Earth’s rotation axis; thus the half-bowl faces south and the gnomon points >> south, but the end of the gnomon that attaches to the bowl points north. >> Am I missing anything? I am also looking to use an analemma-shaped gnomon >> to cast the shadow on the bowl, and at least month lines for the solar >> elevation. The bowl will also have a rod and bracket on the bottom to >> allow it to be rotated for daylight-savings time and for local longitude >> corrections. >> >> >> >> Thanks in advance -- Brad >> >> --- >> https://lists.uni-koeln.de/mailman/listinfo/sundial >> >> >> > --- https://lists.uni-koeln.de/mailman/listinfo/sundial
Re: Hemicyclium correction - a figure might be needed
I can't find an image on the internet, of a Circumference-Aperture Cylinder-Equatorial dial, but I'm going to post a drawing of one. By the way, I use a broad definition of Equatorial Dial. Instead of only dials with a dial-face parallel to the equator, I include all dials that directly measure the Sun's apparent movement parallel to the equator. Well, any dial with a polar style (including the Polar Dial and all the Polar-Gnomon Flat Dials) measures the Sun's movement about the polar axis *reasonably* directly. Maybe all such dials almost qualify as Equatorial then. But I only call a dial Equatorial if it directly measures the Sun's apparent movement parallel to the equator, on a uniform circular scale that measures along a line parallel to the equator. ...even if the dial-face isn't parallel to the equator. Michael Ossipoff --- https://lists.uni-koeln.de/mailman/listinfo/sundial
Re: Sundial books for children
Show them sundials that can be explained to them. I think that people will like something better, enjoy it more, if they know how it works. As much as I like the Analemmatic Dial, I prefer (at least at first) showing people sundials that they'd be willing to listen to an explanation of. ...or dials whose explanation is brief. So, that would rule-out the Analemmatic, and declining flat dials, and altitude dials. The Horizontal Dial, closely derived from the Equatorial Dial, has a brief and intuitive explanation. Likewise the South Vertical Dial, the Polar Dial, and any north or south Reclining Dial. (They're like Horizontal Dials for different latitudes). (They could be summarized as any dial whose plate's normal is in the plane of the meridian). Of course the Equatorial Dials are the most obvious and natural of all, not really requiring explanation. (By "Equatorial", I mean any dial that directly shows a shadow's or lightspot's movement around the equatorial plane by uniformly-spaced marks around a circle in that plane) My favorite for a south windowsill is the Circumference-Aperture Cylinder-Equatorial, but I'd want to include, with it, at least a *description* of the geometric demonstration of its principle. (My girlfriend doesn't care for geometry or math, but she's going to hear about the geometry of a Circumference-Aperture Cylindrical-Equatorial.) Declining flat dials, altitude dials, the Analemmatic Dial, and the Circumference-Aperture Cylinder-Equatorial are good ways of inspiring interest in, and demonstrating, some geometry or astronomical mathematics. Emphasize to the person, that those subjects are relevant and interesting, and useful. It seems to me that those dials would be especially a good idea for school math classes, or for when someone's child is taking such courses. Michael Ossipoff On Sun, Nov 5, 2017 at 10:46 AM, Dan-George Uza wrote: > Hello, > > I am looking for titles of sundial books for children. I particularly > liked Annos sundial pop-up book by Mitsumasa Anno. Also, I would like to > know some of your experiences in working with kids. What do you think is > the best approach to teach 10 year olds about sundials? > > Regards, > > Dan Uza > > --- > https://lists.uni-koeln.de/mailman/listinfo/sundial > > > --- https://lists.uni-koeln.de/mailman/listinfo/sundial
Re: Lithuania wants to abolish DST
Yes, I too have read that the annual change from Standard Time to Daylight-Saving Time is a disruption that people aren't able to adjust to, not even by the end of summer. But should it be left at Standard Time, or at DST? Leave it on Daylight-Savings Time all year, with no time-change. In other words, leave it on advanced-time all year. In most locations, people are up after dark, and rise after sunrise. There's no need for that, We've used our artificial lighting to move away from nature's time, the Sun's time. Changing to all-year advanced-time would be the best way to quickly remedy that mistake. Some people express the concern about children, in midwinter, going to school in the dark,. But being out in evening dark is more dangerous than being out in morning-dark. Evening dark is more dangerous than morning dark. In the morning there's less traffic, and therefore less risk of getting hit by a car. In the morning dark, there are a lot fewer dangerous people out, as compared to evening dark. I suggest that every consideration points to leaving clocks on advanced-time all year. Michael Ossipoff On Fri, Dec 22, 2017 at 3:36 PM, Dan-George Uza wrote: > From the news: > > https://www.euractiv.com/section/health-consumers/news/ > lithuania-hopes-to-kill-daylight-savings-time/ > > Please also note the smiling sundial in the picture. > > Dan Uza > > --- > https://lists.uni-koeln.de/mailman/listinfo/sundial > > > --- https://lists.uni-koeln.de/mailman/listinfo/sundial
Re: The utility of sundials today.
At a time when all watches were mechanical, and a reliable watch wasn't affordable to all, I sometimes used a portable sundial, a compass-oriented tablet-dial made from corrugated cardboard and typewriter-paper, with sewing-thread as the gnomon. No doubt the more easily built Regiomontanus dial would have been useful too (except near noon). Also, the Analemmatic Dial, especially the universal one, makes a good sun-compass. It's a lot easier to carry a piece of paper or cardboard than a compass, and a sun-compass is just as usable in a steel car, bus, train, etc., where a compass would lose accuracy. But of course nowadays a sundial's main value is aesthetic, and that's the the reason for the recent resurgence in the popularity of sundials. Why shouldn't every windowsill have a sundial? Sundials are interesting and pleasant to have around, or run across somewhere, regardless of whether there's practical need. Michael Ossipoff On Sun, Jan 14, 2018 at 2:26 PM, Willy Leenders wrote: > > When I talk about sundials, I get the question: "What utility can sundials > have today?" > In order to be able to give an answer as diverse as possible, I would > like to receive your answer to this question > > > Willy Leenders > Hasselt in Flanders (Belgium) > > Visit my website about the sundials in the province of Limburg (Flanders) > with a section 'worth knowing about sundials' (mostly in Dutch): > http://www.wijzerweb.be > > > > > > > > > --- > https://lists.uni-koeln.de/mailman/listinfo/sundial > > > --- https://lists.uni-koeln.de/mailman/listinfo/sundial
Re: Fwd: Re: The utility of sundials today.
That's true--A sundial shows things that a clock doesn't show, a direct showing of nature's day and year. Michael Ossipoff On Mon, Jan 15, 2018 at 2:55 AM, Kurt Niel wrote: > In some practical matter: > Using sundials you can: > - directly observe behaviour of nature, especially the planetarian > movements > - get in touch with our solar system > - get some analog feeling of time by observing the shadow movement > - check for different parts of movements due to day time deviations > - slow down. > > And so on. > > Kurt > https://kepleruhr.eu > > > 2018-01-15 2:01 GMT+01:00 illustratingshadows < > illustratingshad...@gmail.com>: > >> The study of sundials includes many disciplines. History, Geography, >> Solar system, Geometry, Trigonometry, and from that come an understanding >> of kinds of time, algorithms, hence coding, and related disciplines. The >> seasons and why. And I could go on. Yes, different numbering systems and >> how they affect a nation's paradigms, and how that in turn can limit >> scientific advancement, or, catapult it. >> >> And so on. >> >> The study, rather than the use, of a sundial can legitimately spawn an >> entire curriculum! >> >> Simon >> www.illustratingshadows.com >> >> >> >> Sent from my Verizon, Samsung Galaxy smartphone >> >> Original message >> From: BRIAN ALBINSON >> Date: 1/14/18 16:42 (GMT-07:00) >> To: Sundial sundiallist >> Subject: Fwd: Re: The utility of sundials today. >> >> >> >> >> Forwarded Message >> Subject: Re: The utility of sundials today. >> Date: Sun, 14 Jan 2018 12:34:56 -0800 >> From: BRIAN ALBINSON >> To: Willy Leenders >> >> >> Willy >> >> I think what utility is the wrong question. What utility does the Mona >> Lisa have? >> >> Sundials should be viewed as a living part of the social, cultural, >> astronomical, mathematical and historical record. >> Brian Albinson >> >> On 1/14/2018 11:26 AM, Willy Leenders wrote: >> >> >> When I talk about sundials, I get the question: "What utility can >> sundials have today?" >> In order to be able to give an answer as diverse as possible, I would >> like to receive your answer to this question >> >> >> Willy Leenders >> Hasselt in Flanders (Belgium) >> >> Visit my website about the sundials in the province of Limburg (Flanders) >> with a section 'worth knowing about sundials' (mostly in Dutch): >> http://www.wijzerweb.be >> >> >> >> >> >> >> >> >> >> ---https://lists.uni-koeln.de/mailman/listinfo/sundial >> >> >> >> --- >> https://lists.uni-koeln.de/mailman/listinfo/sundial >> >> >> > > --- > https://lists.uni-koeln.de/mailman/listinfo/sundial > > > --- https://lists.uni-koeln.de/mailman/listinfo/sundial
This year a probe will be sent through the Sun's corona.
Maybe this is a little off-topic here, but not completely: . As you may have heard, a space-probe is scheduled to be launched this month, which will pass through the Sun’s corona (which extends much farther out from the Sun than it was previously believed to). . In other words, NASA is goings to intrusively experiment on the Sun. . This is called the “Parker solar probe”. . Does anyone else find that objectionable? Even just on principle, if for no other reason? . Of course the Sun is the origin and energy-source of the Earth, and therefore the physical origin of all life on Earth. …so we dump our garbage into it? . Is there anything that we respect enough to not spit on it? . After the probe’s first pass through the corona, I don’t know if will be moved out of that corona-traversing orbit. Probably not. If not, the of course each passage will slow the vehicle, until it eventually falls into the Sun, meaning our garbage becomes part of the sun. . Someone told me that the craft might vaporize during its first corona-passage. I don’t know if that’s true, but, even if so, it doesn’t change the experiment’s object. . No, the experiment probably won’t result in an “Oops!”, “Uh-Oh!”, or “Oh Shit!” moment. Probably not. Is “probably not” good enough? . But there are times when a small bit of matter, operating in a small part of a large object, starts an effect that propagates throughout that larger object. No, I’m not saying that’s likely. . The whole justification for the experiment is a lack of knowledge about the Sun, and the corona in particular. How much assurance does a lack of knowledge guarantee? But, in any case, see above for other reasons why the experiment is objectionable. . You go outside. It’s a nice sunny day. The solar-convective breeze is rustling the chlorophyll leaves of the green trees. So, with the warm sunshine warming your face, you say, “Ah yes, let’s intrusively experiment on the Sun, and dump garbage into it!” . Michael Ossipoff --- https://lists.uni-koeln.de/mailman/listinfo/sundial
Re: This year a probe will be sent through the Sun's corona.
Roger said: . [quote] Off topic/ Yes! [/quote] . No, not entirely. . And it isn’t rare here for posts to be precisely on topic by being directly about sundials. . [quote] Please get a grip. [/quote] . Whoa, Cowboy. I clarified that a seriously undesirable unintended result is unlikely. Here’s what I said, in case you missed it: . “No, the experiment probably *won’t* result in an “Oops!”, “Uh-Oh!”, or “Oh Shit!” moment.” …so you’re answering regarding a matter that I already addressed. . [quote] Do you know the void of outer space? [/quote] . Not intimately :D . But it doesn’t bear on what I said. . [quote] Do you realize the immensity of the nuclear fusion reactions fueling the sun. Any probe is infinitesimal in comparison. Do the numbers. [/quote] . My, aren’t we the science expert ! . See above. . Though (as I said in my initial post) a very small local intrusive influence can sometimes start a reaction that propagates throughout a much larger medium, I’ve clarified that I don’t claim that’s likely in this instance. . Life is full of risks, and all of the personal risks that concern people are a lot greater than the risk of an undesired result from the Parker probe. . Every time someone gets in their car, and takes it on the road, the risk to their safety is incomparably greater than the small risk of harm resulting from the solar-probe experiment. . As I thought that I clarified, my objection is about repugnance, not risk. .Here’s what I said: . You go outside. It’s a nice sunny day. The solar-convective breeze is rustling the chlorophyll leaves of the green trees. So, with the warm sunshine warming your face, you say, “Ah yes, let’s intrusively experiment on the Sun, and dump garbage into it!” . Visit an art museum. Go up to a large statue from the Classical Period, and throw a wadded up piece of trash-paper at it. . Then explain to the security guards, “Don’t you know anything about science? That wad of trash-paper doesn’t possess enough mass to knock that much more massive statue over. Nor does it have enough hardness to damage the statue’s surface. Get a grip.” . I’m not anti-science, but I admit that I don’t worship science. . There seems to be a widespread popular belief that if there’s an experiment “for science” that can be done, then we’re obligated, by some notion of scientific-necessity, to do it. . I expressed an opinion. You disagree. Fine. Duly noted. But try to remember civility. . Because I find the intrusive experiment on the Sun to be repugnant, I’ve brought the matter up at several forums. . There’s always someone who will explain to me that the probe is much smaller than the Sun :D . II mentioned the matter here because people here probably aren't unanimously gung-ho about "anything for science". Michael Ossipoff On Fri, Feb 9, 2018 at 12:26 AM, Roger Bailey wrote: > Hello Michael, > > Off topic/ Yes! > > Please get a grip. Do you know the void of outer space? Do you realize the > immensity of the nuclear fusion reactions fueling the sun. Any probe is > infinitesimal in comparison. Do the numbers. This probe is not a violation > of a sacred place. > > Roger Bailey > > *From:* Michael Ossipoff > *Sent:* Thursday, February 08, 2018 4:42 PM > *To:* sundial list > *Subject:* This year a probe will be sent through the Sun's corona. > > > Maybe this is a little off-topic here, but not completely: > > . > > As you may have heard, a space-probe is scheduled to be launched this > month, which will pass through the Sun’s corona (which extends much farther > out from the Sun than it was previously believed to). > > . > > In other words, NASA is goings to intrusively experiment on the Sun. > > . > > This is called the “Parker solar probe”. > > . > Does anyone else find that objectionable? Even just on principle, if for > no other reason? > > . > > Of course the Sun is the origin and energy-source of the Earth, and > therefore the physical origin of all life on Earth. …so we dump our > garbage into it? > > . > > Is there anything that we respect enough to not spit on it? > > . > > After the probe’s first pass through the corona, I don’t know if will be > moved out of that corona-traversing orbit. Probably not. If not, the of > course each passage will slow the vehicle, until it eventually falls into > the Sun, meaning our garbage becomes part of the sun. > > . > > Someone told me that the craft might vaporize during its first > corona-passage. I don’t know if that’s true, but, even if so, it doesn’t > change the experiment’s object. > > . > > No, the experiment probably won’t result in an “Oops!”, “Uh-Oh!”, or “Oh > Shit!” moment. Probably not. Is “probably not” good
Yes to year-round advanced-time
It would be better to stay on advanced-time (Daylight Saving Time, Summer-Time) year-round. The change from Standard Time to Daylight Saving Time results in increased numbers of accidents of all kinds, because everyone's schedule is disrupted by having to get up an hour earlier. It has been determined that, throughout the Daylight Saving Time months, people never get used to that schedule disruption. So, we should keep one kind of time all year. But which one--Standard or Daylight Saving? I say keep Daylight Saving Time all year. For one thing, it's better start the day earlier, and do things earlier in the day. Besides, our schedule has been artificially skewed by artificial lighting: For the most part, we start our day some time after sunrise, or at least long after the beginning of Civil Twilight, and then end our day long after dark. Our schedule has moved away from nature's solar time. Year-round advanced time (Daylight Savings Time or Summer-Time) would move our schedule back in the right direction. We hear concern about children going to school in the dark, in winter, if we had DST all year. But, as I've pointed out before, being out in morning dark is a lot safer than being out in evening dark. That' because evening dark has more traffic, and more dangerous people out and about. So, contrary to those safety-based arguments against year-round DST, such a system would be safer. Michael Ossipoff --- https://lists.uni-koeln.de/mailman/listinfo/sundial
