Re: Knowing where we are
Chris, Thanks for responding to Doug's query and correcting my incorrect response. It is continually amazing to me how well this software works (on a Garmin GPS system and Microsoft Streets) both in routing between two points and Streets in optimizing multipoint routes. Gordon Uber At 03:20 AM 7/21/2008, Chris Lusby Taylor wrote: Hi Doug, The task of finding the shortest/quickest route from A to Z along a network of roads is not the same as the Travelling Salesman Problem, nor its generalisation the Vehicle Routing Problem, unless you also say you want to go via C, D, E etc in no particular order but without visiting any of them twice. Your GPS is usually solving the very much simpler problem of merely finding the shortest/quickest route from A to Z. To do this, all it needs to do is to find the distance to all the crossroads you can reach directly from A, then the minimum distance to all the crossroads you can reach from them, and so on until you find yourself at Z by one route and all other routes that haven't yet reached Z are already longer. By the way I'm sure it does use vectors, not bitmaps, to draw the route, and a table of the properties of all road segments. This may still be a substantial task, and there are ways to direct the search to improve the chances that the first route you try will be the best. For instance, you can use a 'meet in the middle' approach - fan out from both A and Z until you find paths that meet. Either way, it can then use a critical-path type analysis to see which is/are the shortest route(s). For instance, if C is 20 miles from A, D is 25 miles from A but the road CD is 6 miles long, it cannot be on the shortest route. However, I do have a GPS that can tell me how to get from A to Z via B and C, where B and C are visited in any order to minimise the total journey. That is the Travelling Salesman Problem, near enough. Best wishes Chris --- https://lists.uni-koeln.de/mailman/listinfo/sundial
Re: Knowing where we are
Hi Doug, Look up vehicle routing problem and the following: http://www.sintef.no/static/am/opti/projects/top/vrp/ Here is a list of research papers available on line: http://www.sintef.no/static/am/opti/projects/top/vrp/bibliography.html Your assumption is basically correct. The solution must be searched for. In general, given a table of nodes/intersections and the distances between them, one can search all paths for the shortest path. Since this usually takes too long, one takes shortcuts (heuristics or guesses), sometimes not even attempting the best solution. (I was looking at this in about 1963 for finding the shortest length of wire to interconnect a set of electrical terminals. I have not kept up in the field.) Gordon At 01:34 PM 7/20/2008, Douglas Bateman wrote: Sundiallists always know where they are, but do they know where they are going? This rather rhetorical question is slightly off topic and directed to our computer experts: the question is how does my satellite navigation (Sat Nav) system in my car, or hand held, know where it is going and how to get there when I give it an address? A search in Wikipedia or Google under satellite navigation talks about the satellites, timing, position, etc, but NOT what is in my little box. I assume that the memory holds some form of map (vector storage, or bit map?) and a series of nodes for every single road intersection (and plans thereof). A route finding algorithm must exist for testing all the nodes between and A and B. I also assume each link between any two nodes must obey some rules about speed limits, preferences for motorways, etc. Then, I assume that the incoming signal for latitude and longitude must cause the map to 'place itself' under this lat long so that you can see a real time display of where you are and where you are going. It would be nice to know more! Any advice please. Regards, Doug (who sometimes still get lost) --- https://lists.uni-koeln.de/mailman/listinfo/sundial --- https://lists.uni-koeln.de/mailman/listinfo/sundial
Re: Equation editor software
Doug, Another option is MathType by Design Science. It claims to be an extended version of the Microsoft Equation Editor, so it may have the same problems that your editor is already encountering. It worked for me when I last used it about five years ago. Gordon At 03:02 AM 6/19/2008, Douglas Bateman wrote: Slightly off topic, but I am enquiring about suggestions for a package of modest capability. The background is that I offered to assist the editor of a related publication to sundials - Horological Journal. (The British Horological Institute has just celebrated its 150th anniversary.) The editor has a journalistic training and uses Quark publishing. Material often comes to her in Word, and it seems that equations do not transfer reliably. Suggestions will be appreciated. Regards, Doug --- https://lists.uni-koeln.de/mailman/listinfo/sundial --- https://lists.uni-koeln.de/mailman/listinfo/sundial
Re: Oldest sundial in world ?
Richard, From Marshall Clagett's Ancient Egyptian Science Vol. 2, earliest extant Egyptian shadow clock(Cairo Museum, time from length of shadow) is 1479-1425 BC. Earliest extant (vertical disk) sundial (from Gezer in Palestine) is 1224-1214 BC. I don't know dates for Babylonian dials. The Karnak water clock is earlier: 1391-1353 BC, description of similar clock from 1525-1504 BC. Star positions were used for nighttime hours by the 24th century BC, evolving into star clocks by 2150 BC (tables of constellations for each hour and week). Gordon Uber San Diego, California At 11:41 AM 5/30/2008, Richard Mallett wrote: When I was buying the set of cigarette cards issued in 1928 by W.D. and H.O. Wills of Old Sundials, my dealer asked me what was the oldest sundial in the world ? I guessed Greek or Roman, but didn't really know; so input from the experts on this list would be welcomed. -- Richard Mallett Eaton Bray, Dunstable South Beds. UK --- https://lists.uni-koeln.de/mailman/listinfo/sundial
Re: temporary hours
Ronit, Egyptian practice after about 2150 BCE was to have twelve daytime hours and twelve nighttime hours. Daytime hours were determined by shadow clocks (based on the sun's angle east or west of the zenith meridian), nighttime hours by star clocks and water clocks. Star clocks were based upon the heliacal rising (and in later years upon the meridional transit) of 36 decans (groups of stars), and upon their visibility after sunset. It appears to me that at least the nighttime hours were principally used for timing religious activities. For references see the Wikipedia entry on water clocks. The most comprehensive work that I have found on Egyptian timekeeping is Marshall Clagett's source book: Clagett, Marshall, Ancient Egyptian Science, Volume II: Calendars, Clocks, and Astronomy, 1995, Memoirs of the American Philosophical Society, Vol. 214, Philadelphia. Gordon Uber, San Diego, California At 04:11 PM 5/20/2007, Noam Kaplan wrote: Ronit, Depends what you mean by antiquity. For everyday use in the Roman and Greek world as far as I know the night was divided into watches, vigils. In the Talmud there is an argument as to how many watches the night is divided, three or four. But there were definitely methods of timekeeping to - Original Message - From: mailto:[EMAIL PROTECTED]øåðéú îòåæ To: mailto:[EMAIL PROTECTED][EMAIL PROTECTED] Sent: Sunday, May 20, 2007 8:44 PM Subject: temporary hours Dear friends, Was the division of day+night in antiquity divided into 12 temporary hour day and 12 temporary hour at night thanks in advance for your answers. Ronit Maoz -- --- https://lists.uni-koeln.de/mailman/listinfo/sundialhttps://lists.uni-koeln.de/mailman/listinfo/sundial --- https://lists.uni-koeln.de/mailman/listinfo/sundial --- https://lists.uni-koeln.de/mailman/listinfo/sundial
Re: Russell Porter sundial
Mac, I suspect that if you aim the telescope at the sun then the hour circle will show the local time. In Porter's (Scientific American) Amateur Telescope Making, probably Volume I, there is a sketch of a sundial based on a spherical chemist's flask. As I recall, a lens in the neck was aimed at the sun which would be focused on the date on the analemma strip in the center. I was tempted to build one, but never did. Gordon Uber (who ground--and almost polished--a telescope mirror as a fifteen-year-old) At 04:45 PM 5/14/2007, Mac Oglesby wrote: Hello Friends, The Summer 2007 issue of Vermont Life magazine contains a nice article on Stellafane, a convention of amateur telescope makers which convenes each summer in Vermont, USA. Prominent among its founders was Russell W. Porter, architect, artist, mechanical genius, Arctic explorer, telescope maker, and dialist. A sidebar features Porter's Garden Telescope, described as an elegant combination of a sundial and a reflecting telescope. A replica is being produced by Fred and Russ Schleipman of Norwich, Vermont. Point your browser at: http://www.gardentelescopes.com/ (be sure to read the History and About Us pages) Porter designed and produced several different cast bronze sundials. Some may be owned by members of this List. My question is, how, exactly, does the elegant device pictured in the magazine (and on the website) function as a sundial? Best wishes, Mac Oglesby (Who, 60+ years ago, was walking round and round the barrel, trying to make a reflecting telescope mirror.) --- https://lists.uni-koeln.de/mailman/listinfo/sundial --- https://lists.uni-koeln.de/mailman/listinfo/sundial
Re: Best Photos for Hi Def TV
John, The highest-resolution specified HDTV format is 1920 wide by 1080 high 16:9 widescreen format). Note that the HDTV specification defines many, many resolutions and formats. I think that this should be adequate for present and future work, and it would permit you to reformat later for full resolution. However, I think that DVD, broadcast and cable HDTV are currently less than this, typically 720p (progressive), 1280 x 720 resolution. Current DVD formats do not support full HDTV, and the HD-DVD vs. BluRay DVD battle is still being waged. For a computer display at the nominal 100 dpi PC display resolution this would correspond to a 20 by 11 inch display, which few people now have. I do not know what resolutions Windows Media Player and Flash support. If you are going to project this for group viewing, then check the specs for digital projectors. If you are going to crop your photos then the digital camera resolution should be correspondingly higher. I would suggest that you capture images to support the highest resolution (thus supporting future upgrades) and that you then reformat for the equipment that you are currently using. Good luck! Gordon http://computing-dictionary.thefreedictionary.com/DTV http://computing-dictionary.thefreedictionary.com/HDTV --- https://lists.uni-koeln.de/mailman/listinfo/sundial
Re: Slightly off-topic: names of geomteric shapes
Hi John, I think you could use some variation on open cylindrical shell segment. A Google (Book) Search for this should locate page 137 with an illustration in _Hybrid and Incompatible Finite Element Methods_ by Theodore H. H. Pian and Chang-Chun Wu. Sorry that it is not one or two words as you wished, but you can refer to it as segment in subsequent discussion. In your definitions of sector and segment you may wish to substitute disk for circle. A mechanical engineering handbook may have some of the future shapes you need. Gordon Uber San Diego At 07:25 PM 10/14/2006, John Pickard wrote: Good afternoon everyone, This is a bit off-topic, but given the range of expertise available on the Sundial List, I think I can get an answer ... I need names for some geometric shapes for some research I am doing. Two are not a problem: Sector: a part of a circle bounded by the circumference and two radii meeting at the centre of the circle. Segment: a part of a circle bounded by the circumference and a chord. But is there a simple one- or two-word name for a piece of a pipe? Imagine a pipe cut lengthwise with two radial cuts to give a long piece which in cross section is bounded by two arcs, joined by the radii. Is there a formal name for this shape? It's only the two-dimensional shape that interests me, i.e. the cross-section of the bit cut lengthwise out of the imaginary pipe. I guess it could be a pipe sector , but this doesn't sound very mathematical! More generally, does anyone know of a web source with diagrams of numerous geometric shapes and their names? I think I will have a few more odd cross-sections come up in the next few months, and I will need names for them. Cheers, John John Pickard mailto:[EMAIL PROTECTED][EMAIL PROTECTED] --- https://lists.uni-koeln.de/mailman/listinfo/sundial --- https://lists.uni-koeln.de/mailman/listinfo/sundial
Re: Exact Time and date conventions
The standard practice for insect specimen labels has been to use Roman numerals for the month to avoid ambiguity. This was true fifty years ago. However, some recommend a three- or four-letter English abbreviation for the month (see below). ttp://members.aol.com/YESedu/collect3.html A locality label (see below) should accompany each beetle specimen, whether pinned, pointed, or in alcohol. The label should contain the following information: location (state, county and nearest town or other permanent landmark), date(s) of collection, and the name of collector(s). When writing the date on a label, use one of the two following formats: 11 SEPT 1993 or 11-ix-1993. If you use 11-9-93 for the date, other collectors will not be sure if you meant November 9th or September 11th. http://www.biology.ualberta.ca/bsc/pdf/labelbrief.pdf Gordon Uber At 01:22 AM 4/6/2006, Douglas Bateman wrote: The British Post Office uses something similar except that Jul becomes Jly. I looked at the postmarks on 3 letters that I received this morning and to my DISMAY they have used 3 methods. One has the old style round franking stamp with the date 4 APR 2006, another has gone through an inkjet type of franking that gives the date as 05.04.06 and the third, also with a round franking, gives 5 -IV 2006. Note that the Roman numeral for the month is also unambiguous, which I recall as being an informal European method. --- https://lists.uni-koeln.de/mailman/listinfo/sundial
Re: Save the Leap Second
From the figures in the Metrologia article, about half of the effect is due to tidal I would think a manua At 22:28 7/13/05, Thaddeus Weakley wrote: If there was a table or formulaic way of predicting the growing time decrepancy over years, decades, etc. then correction for the proper fraction of an hour error could just be incorporated into the equation of time. I believe (esp. over long time frames) this would be as predictable as the location of heavenly bodies on any given night. I still vote for keeping the leap second though. Thad Weakley 42.2N 83.8W Gordon Uber [EMAIL PROTECTED] wrote: Sundial List; Having thought about it intermittently for all of a day, I think that the leap hour is an acceptable approach to civil time. The changes, taking place over generations between leap hours, are slow enough so that the people can adjust. The leap hour itself is no greater than Daylight Saving Time changes in many regions. (There is no Daylight Saving Time in Hawaii or Arizona, among other places; people living there will be in for a shock when the leap hour occurs.) I suggest that most sundials today are used for less than a century and that the accumulated error of several minutes within that interval after manufacture is acceptable to most casual users. The dialing community would have the challenge of incorporating an offset of up to plus or minus one-half hour in an interesting, convenient and useful ! way so that dials can be accurate over many centuries. I have great confidence that it can be done. Perhaps a sundial design contest would be appropriate -- should the leap hour be adopted. Looking back over the last millennium or two, I find it daunting to predict sundial designs and timekeeping itself a millennium into the future. Anyone care to try? Both books on Daylight Saving Time listed below are interesting. I recommend them to the list. Seize the Daylight gives a more global perspective of the two, and it therefore may be of somewhat greater interest to those on this list. Gordon Uber San Diego, California Date: Tue, 12 Jul 2005 14:10:10 -0700 To: sundial@rrz.uni-koeln.de From: Gordon Uber Subject: Re: Save the Leap Second Sundial List, Having read two recent books on the tumultuous history of Daylight Saving Time (Seize the Day! light and Spring Forward), I think that a one-hour difference between zone time and sun time may be too large, even if it will not occur in my lifetime. Of course, it may be considered to be plus or minus one-half hour. Clock setting is already becoming increasingly automatic with radio-controlled and GPS clocks and time displays on mobile phones. Therefore I don't see a major problem for the typical person with respect to clock setting a millennium hence with either leap seconds or leap hours for civil time. Either will be incorporated into the time distribution and display systems. Missing the equivalent of a favorite TV program or an hour of wages will be more contentious. Gordon Uber San Diego, California - __ Do You Yahoo!? Tired of spam? Yahoo! Mail has the best spam protection aro! und http://mail.yahoo.com -
Re: Save the Leap Second
Having thought about it intermittently for all of a day, I think that the leap hour is an acceptable approach to civil time. The changes, taking place over generations between leap hours, are slow enough so that the people can adjust. The leap hour itself is no greater than Daylight Saving Time changes in many regions. (There is no Daylight Saving Time in Hawaii or Arizona, among other places; people living there will be in for a shock when the leap hour occurs.) I suggest that most sundials today are used for less than a century and that the accumulated error of several minutes within that interval after manufacture is acceptable to most casual users. The dialing community would have the challenge of incorporating an offset of up to plus or minus one-half hour in an interesting, convenient and useful way so that dials can be accurate over many centuries. I have great confidence that it can be done. Perhaps a sundial design contest would be appropriate -- should the leap hour be adopted. Looking back over the last millennium or two, I find it daunting to predict sundial designs and timekeeping itself a millennium into the future. Anyone care to try? Both books on Daylight Saving Time listed below are interesting. I recommend them to the list. Seize the Daylight gives a more global perspective of the two, and it therefore may be of somewhat greater interest to those on this list. Gordon Uber San Diego, California Date: Tue, 12 Jul 2005 14:10:10 -0700 To: sundial@rrz.uni-koeln.de From: Gordon Uber [EMAIL PROTECTED] Subject: Re: Save the Leap Second Sundial List, Having read two recent books on the tumultuous history of Daylight Saving Time (Seize the Daylight and Spring Forward), I think that a one-hour difference between zone time and sun time may be too large, even if it will not occur in my lifetime. Of course, it may be considered to be plus or minus one-half hour. Clock setting is already becoming increasingly automatic with radio-controlled and GPS clocks and time displays on mobile phones. Therefore I don't see a major problem for the typical person with respect to clock setting a millennium hence with either leap seconds or leap hours for civil time. Either will be incorporated into the time distribution and display systems. Missing the equivalent of a favorite TV program or an hour of wages will be more contentious. Gordon Uber San Diego, California -
Re: Save the Leap Second
Having read two recent books on the tumultuous history of Daylight Saving Time (Seize the Daylight and Spring Forward), I think that a one-hour difference between zone time and sun time may be too large, even if it will not occur in my lifetime. Of course, it may be considered to be plus or minus one-half hour. Clock setting is already becoming increasingly automatic with radio-controlled and GPS clocks and time displays on mobile phones. Therefore I don't see a major problem for the typical person with respect to clock setting a millennium hence with either leap seconds or leap hours for civil time. Either will be incorporated into the time distribution and display systems. Missing the equivalent of a favorite TV program or an hour of wages will be more contentious. Gordon Uber San Diego, California -
Re: Save the Leap Second
Here are a few articles, not necessarily any which meet your requirements: The future of leap seconds, including link to Meeus's article http://www.ucolick.org/~sla/leapsecs/onlinebib.html Survey article on leap seconds http://www.ucolick.org/~sla/leapsecs/ The Leap Second: Its history and possible future http://www.cl.cam.ac.uk/~mgk25/time/metrologia-leapsecond.pdf There is also a note elsewhere from Signal Engineering regarding DCPRS Certification (whatever that is): that a GPS receiver must be turned on from Standby Mode for at least 12.5 minutes before use so that the GPS Almanac can be downloaded to determine if a Leap Second had occurred. I wonder if eliminating the Leap Second would permit faster startup. Gordon Uber San Diego, California At 15:48 7/11/05, Brian Albinson wrote: Frank Could you either explain in a couple of lines, or direct me to a site which provides an explanation comprehensible to an old engineer, what is the big problem in inserting leap seconds?? Brian Albinson 49.33, 123.06 -
Re: mean time
pp. 74-6: However, the sun's motion in right ascension [along the celestial equator] is not uniform because the Sun moves in the ecliptic rather than the equator, and the Sun's motion in the ecliptic is not uniform [due to elliptical orbit]. Mean solar time was defined by an abstract fiducial point ... fictitious mean sun ... to move uniformly in the equatorial plane at a rate that is virtually equal to the mean rate of the true Sun's motion in the ecliptic. The difference between mean solar time and apparent solar time is called the equation of time. At least formerly, solar time was computed from observed sidereal [star] time. What is today called Greenwich Mean Time (civil time) in the UK is actually Coordinated Universal Time for the Greenwich time zone. It is kept by atomic clocks and modified by leap seconds as required by variations in the Earth's rotation. I am guessing that the observed noon (sun due south or at its highest altitude) defined 12:00 noon for apparent solar time at Greenwich. For those interested in this topic, this book has a sixty-page chapter on time, including its history. From Astronomical Algorithms by Jean Meeus, p. 379, The mean solar time is the hour angle of the mean sun , and this is measured from mean noon. The civil time is the mean solar time increased by 12 hours, and thus is measured from mean midnight. Gordon At 11:42 6/10/05, Noam Kaplan wrote: Does anyone know how mean time is set up? To clarify, I know that local mean time has 24 hours every day set for a mean daily rotation for any particular location. I understand that timezones are set up by the local mean time for the center of every 15 degrees of longitude, i.e. 0, 15, 30, 45 etc. What I don't understand is how was it chosen when 12:00 AM/PM would be. I used to think that mean time was set by the equinox that midday was 12:00 for the whole year. This is obviously incorrect as the equation of time which shows how much local mean time is off from apparent solar time is not 0 at 12 on the equinox. If anybody can explain to me what and how mean time was set up, I would appreciate it. Thanks, Noam Kaplan N 40.5833 W 74.1166 Staten Island -
Re: Naked eye astronomy?
Here are some quick answers for you without looking up detailed references.
Hope that this helps.
http://www-groups.dcs.st-and.ac.uk/~history/Mathematicians/Hipparchus.html
Perhaps the discovery for which Hipparchus is most famous is the
discovery of precession which is due to the slow change in direction of the
axis of rotation of the earth. This work came from Hipparchus's attempts to
calculate the length of the year with a high degree of accuracy. There are
two different definitions of a 'year' for one might take the time that the
sun takes to return to the same place amongst the fixed stars or one could
take the length of time before the seasons repeated which is a length of
time defined by considering the
http://www-groups.dcs.st-and.ac.uk/~history/Mathematicians/javascript:win1('../Glossary/equinox',350,200)equinoxes.
The first of these is called the
http://www-groups.dcs.st-and.ac.uk/~history/Mathematicians/javascript:win1('../Glossary/sidereal_year',350,200)sidereal
year while the second is called the
http://www-groups.dcs.st-and.ac.uk/~history/Mathematicians/javascript:win1('../Glossary/tropical_year',350,200)tropical
year.
Of course the data needed by Hipparchus to calculate the length of these
two different years was not something that he could find over a few years
of observations. Swerdlow [19] suggests that Hipparchus calculated the
length of the tropical year using Babylonian data to arrive at the value of
1/300 of a day less than 365 1/4 days. He then checked this against
observations of equinoxes and
http://www-groups.dcs.st-and.ac.uk/~history/Mathematicians/javascript:win1('../Glossary/solstice',350,200)solstices
including his own data and those of
http://www-groups.dcs.st-and.ac.uk/~history/Mathematicians/Aristarchus.htmlAristarchus
in 280 BC and Meton in 432 BC. Hipparchus also calculated the length of the
sidereal year, again using older Babylonian data, and arrived at the highly
accurate figure of 1/144 days longer than 365 1/4 days. This gives his rate
of precession of 1 deg per century.
* N M Swerdlow, Hipparchus's determination of the length of the
tropical year and the rate of precession, Arch. Hist. Exact Sci. 21 (4)
(1979/80), 291-309.
J Norman Lockyer evaluated Egyptian temple alignments in his book The Dawn
of Astronomy, MIT Press, Cambridge, MA, 1894, reprinted 1964. He gives
temple orientations vs. date of construction, and he also discusses
pyramids. His magnetic azimuth measurements are accurate to at best 1/4
degree. The temple of Amon Ra (Re) at Karnak is accurately aligned to the sun.
http://www.crystalinks.com/gpstats.html
Gives dimensions, alignments and angles for the Great Pyramid, but no
scientific analysis.
Naked eye astronomical measurements (with graduated instruments) reached
their greatest accuracy with the plain sights of Tycho Brahe and Johannus
Hevelius: accuracy on the order of 30 for stars or the sun. Ptolemy and
earlier astronomers used peephole sights, which were less precise.
Plain sights are an interest of mine and I would be happy to discuss them
with anyone interested.
Gordon Uber
San Diego
At 02:06 2/18/05, anselmo wrote:
Dear dialists,
Yes, I know this is old hat, but
does anybody know how could Hipparcus
know the longitude of a tropical year
with a 4-digit precission? More
generally, which is the highest
accuracy one can expect from naked-eye
observations to equinoxes, solstices,
NSEW points, and so on... Is it true
that some egyptian temples are aligned
up to the arc-minute or is it just
science-lore?
Regards,
Anselmo
-
Re: ENC: Magnetic Gnomon Attachment
The temperature above which demagnetization occurs is called the Curie point. This is listed for many materials. For example, it can be as low as 25 deg C for monel (nickel copper alloys) to as high as 1121 C for cobalt. Nickel-iron alloys are in the range 300-500 C; iron is 770 C. I think that temperatures well under the Curie point will not demagnetize even after long periods. Gordon At 12:19 2/1/05, Vanderlei Borsari wrote: Dear All, I was thinking about the effect of high temperature on the magnet. I know that very high temperatures can destroy the magnetic power, but what about temperatures around 35 or 40ºC, day after day? Vanderlei Borsari 23.5 S 46.5 W -
Re: the care and feeding of analemmas
I think that you would want a constant distance from a simple lens to the surface so that the sun will always be in focus. This would result in a concave spherical surface bearing the analemma, with the lens at its center. However, if you prefer a flat surface, I think that you can use a photographic lens, these being designed to image onto flat surfaces. Gordon Uber San Diego At 17:53 12/7/04, Aten Heliochronometers wrote: Hello group, I am new here, but have been reading the posts for a few days. I have a question for the group, I am designing a new heliochronometer (afterwards to be referred as a helio for brevity) and I am striving for a bit more accuracy. Roughly, I intend to try and cast a point of light on a surface that contains an analemma. Should I create the analemma on a flat or bowl shaped surface? In other words would it be more accurate to project the analemma onto a plane or a section of a concave sphere? I am mainly concerned with the 47deg. motion of the sun over the course of the year. TIA for any thoughts Dave G. -
Stonehenge replicas in US
fascination for making replicas of Stonehenge. Here are a few. Not traditional sundials, of course. A near-full-size replica of Stonehenge, built this last June at the University of Texas of the Permian Basin. www.odessahistory.com/menusthg.htm photos Brief histories of the project: http://www.mywesttexas.com/site/printerFriendly.cfm?brd=2288dept_id=545240newsid=13108046 http://www.oaoa.com/news/nw060604b.htm Another Texas replica, Stonehenge II, near San Antonio http://www.texastwisted.com/attr/stonehenge2/ A Fortine, Montana replica (with links to slide show). Perhaps the prettiest setting. http://www.andersonmasonryinc.com/stonehenge.php Gordon -
Re: Egyptian obelisks used as sundials?
Thank you very much for your many references and your bringing up Babylonian astronomy, which I had not considered. It is interesting that the Greeks seem to be influenced more by the Babylonians than by the Egyptians. Since my earlier post I have read a bit more myself. Otto Neugebauer in The Exact Sciences in Antiquity refers to a sun dial described in the cenotaph of Seti I in 1300 BCE. But Marshall Clagett shows that this is actually the standard shadow clock, not a sun dial in the modern sense. He also describes a small vertical-plane sun dial (a 2.25 disk with 13 angle markings at 15-degree intervals) from Gezer (1224-1214 BCE). He discusses Ptolemy's analysis of the vertical gnomon. However, there is no direct mention of obelisks as shadow clocks or gnomens. Of course, any marks of hours on the ground could have easily been lost. For you and others interested in Egyptian time keeping I recommend Marshall Clagett's authoritative source book Ancient Egyptian Science, Vol. II, Calendars, Clocks and Astronomy, Memoir Vol. 214, American Philosophical Society, Philadelphia, 1995. I have still found nothing linking Eqyptian obelisks to sundials or timekeeping. Gordon At 07:42 8/21/04, Gianni Ferrari wrote: I try to write some reasons for which I think that the Egyptians has never used the obelisks as sundials 3000 years before Greeks . Herodotus (484-424 B.C.) is the first author that makes mention of the gnomon with the meaning of sundial : Greeks have learned from the Babylonians the polos and the gnomon, as the twelve parts and day (Hist. II). The invention of the first sundials is often attributed to the philosophers Anaximander (610-545 B.C.) and Anaximenes (586-525 B.C.) but certainly the gnomon, simply made by a pole vertically fixed to a horizontal plane, was known and used by he Babylonians. According to some modern researchers (for ex. Szabo, Maula in L' astronomie chez le grecs) it is almost sure that the gnomon was not used in the period 3-400 B.C. as element of a sundial but only as calendrical instrument - to find the beginning of the different seasons - and as astronomical instrument for the determination of the days of the solstices and of the equinoxes, of the length of the inter-solsticial arc (and therefore of the ecliptic inclination) and of the gnomonic equinoctial ratio (ratio between the gnomon's height and the length of its shadow at noon on the equinoxes) that was used in antiquity instead of our modern latitude (as in Vitruvius). Therefore the gnomon did, some century before our epoch, the same functions of the great camera obscura sundials built, as great astronomic hinstruments, in the XVII century. Almost certainly the sundials of Anaximander and Anaximenes, built for different purposes, could only mark the noon or the passage of the Sun on the Southern meridian . Gianni Ferrari 44° 39' N 10° 55' E Mailto : [EMAIL PROTECTED] -
Egyptian obelisks used as sundials?
I have seen vague mention of Egyptian obelisks being used as gnomons for sundials, with hours marked on the ground, perhaps as early as 3500 BCE. No details have been given. If anyone could supply any details (description, location, citation) or could point me in a helpful direction it would be very greatly appreciated. The only early sun clock I have been able to find comprises a bar casting a shadow on a calibrated cross bar, circa 1500 BCE. The obelisks I have been able to find seem to be only monumental. I have seen a list of hourly hymns (both day and night) from the temple of Amun-Ra (or Re) at Karnak circa 1500 BCE; the temporal hours must come from somewhere, with the Karnak clepsydra being a possible source for the night hours. Reference: The Cult of Ra by Stephen Quirke, 2001, containing hymns published by Jan Assmann. Gordon Uber San Diego, California -
Turtle Bay Sundial Bridge opens
A 217-foot bridge pylon forms the gnomon of a sundial. The Sundial Bridge, by Spanish architect Santiago Calatrava, across Sacramento River at Redding, California, opens today. I think that the dial face is marked on a plaza at the end of the bridge. http://www.turtlebay.org/sundial/sundial.shtml This article has many large images of the structure. A Google search will locate other articles, but I could find no others as well illustrated. Gordon Uber San Diego, California -
Re: Off topics - Re: QBasic (was: Right Ascension)
As long as we're trying to top each other in computer seniority My first computer program, in college for an IBM 650, was written in 1955. Later, at Univac, I too programmed several drum-based computers (for example, the water-cooled Univac 1103, which also had a core memory) and other computers in assembler and in numeric machine code. (St. Paul, Minnesota had cold well water all year that was directly piped through the heat exchanger and then to the sewer.) My supervisor forbid the use of an assembler because it would permit us to stray too far from the numeric computer code displayed on the console. Octal (three-bit number) programs for one developmental computer were punched into three levels of perforated paper tape. Paper tape output, too. Biography and employment history: http://www.ubr.com It's fun to hear from those who go back to those early days. Gordon Uber San Diego, California At 09:19 1/16/04, you wrote: Message text written by INTERNET:sundial@rrz.uni-koeln.de I have begun to program for my degree thesis, in 1965 in Bologna University in (Italy).Gianni Ferrari You really have started something here Gianni!! All off topic of course but I started on a Ferranti Pegasus Computer (drum memory machine too) which used valves (vacuum tubes), was water cooled and took up a whole room. We programmed it with its own machine code and also Autocode. All output was on 5-hole paper tape. Those were the days...1959/60. Patrick - -
Re: Sundial inside a room, but room is inside a canyon!
For more on mirror objectives, here is an article on using automobile hubcaps and parabolic L'eggs containers as reflectors. http://www.versacorp.com/vlink/jcart/allsky.htm Fisheye photographic lenses are another option, but expensive. Some early wide-angle camera lenses (for example, the Hill Sky Lens of 1926 for photographing clouds) used a glass hemisphere as the first lens element. This evolved into modern wide-angle and fisheye lenses. http://360vr.com/fisheye41/coastal-fisheyep.pdf I can envision using a wide-angle lens or mirror to form an image of the sky, a relay lens to form a second image of the sky in a room below, and a second reversed wide-angle lens in the room below to project an inverted image of the sun into the room. More simply, the second image could be projected onto a grid to show the time. Gordon Uber At 22:55 1/8/04, Edley McKnight wrote: Hi Tom, shadow watchers, A mirror objective might indeed work. Basically converting the large angular movement of the sun into a much narrower angle at the top and then re-expanding the angles at the bottom. This would be a curved mirror of course, or a set of small mirrors. Approximating it by a set of small mirrors would probably give insight to the proper curved mirror required. Essentially focusing all the sun's movement into a near column down the tube and then dispersing it again at the bottom. A double curving three dimensional mirror seems like it would be needed to keep from shadowing itself during part of the day. Thinking in terms of 'optical levers' might help. Is there an optical engineer of such caliber on board? -
RE: SGS Gnomon Attachment
examination) are routinely made by breaking plate glass (newer knives may be made of diamond). http://www.2spi.com/catalog/knives/glass.shtml http://www.pelcoint.com/glass_html/glassacc.htm And here I thought that Babbage's method was meant to be a joke. Gordon At 09:18 7/28/03 -0600, Rodney E Heil wrote: In ~1988, I attended a lecture at the University of Colorado on the topic of breaking glass. A professor there had studied the subject in depth. I think he was an archeology professor who started by studying how Native Americans made arrowheads (obsidian being very similar to glass). He might have had a grant from the medical industry, because he proposed scalpels made of broken glass for delicate eye surgery. It turns out that broken glass is 100 times sharper than a razor blade. On Mon, 28 Jul 2003 [EMAIL PROTECTED] wrote: Andrew James wrote: According to Charles Babbage in his autobiographical Passages from the Life of a Philosopher (I think, or possibly the Ninth Bridgwater Treatise - it's many years since I read it) there is a simple technique for making a neat hole in a glass sheet using only a centre punch and a hammer (gently!). Gordon Uber [EMAIL PROTECTED] San Diego, California USA Webmaster: Clocks and Time: http://www.ubr.com/clocks -
Re: Obelisk as first sundial?
obelisks for showing time. It had bothered me that while they could be used for timekeeping in Egypt I saw no statements that they were in fact used for this purpose (as opposed to just being a monument). Any further information is welcome. Gordon At 16:36 6/29/03 -0400, you [Patrick Powers] wrote: Message text written by INTERNET:sundial@rrz.uni-koeln.de I have seen references to Egyptian obelisks, built circa 3500 BCE, being used as sundials, or as a minimum to divide the day into morning and afternoon. I would be most grateful if someone could provide a citation for this. When were obelisks first used for sundials? Sarah Symonds (BSS Bulletin 98.3, pp30-36) discussed 'Egyptian Shadow Clocks'. In that article she notes that the obelisk, whilst a popular candidate for a time keeping device does not seem to have been used by the Egyptians in the New Kingdom (1550-1307 BC) . The major argument against their use for time keeping appears to be that most such are covered in inscriptions many of which describe why they were erected. No text yet discovered suggests their use as a time measuring device even though there was room to do so. The shadow clock therefore appears to predate the use of a vertical obelisk gnomon for formal solar timekeeping purposes. Nonetheless, Isler M 'The Gnomon in Egyptian Antiquity', JARCE 28, pp155-185 (1991) mentions the use of staffs and sceptres carried by individuals and possibly used as timekeepers. Does this help? Patrick - Gordon Uber [EMAIL PROTECTED] San Diego, California USA Webmaster: Clocks and Time: http://www.ubr.com/clocks -
Obelisk as first sundial?
I have seen references to Egyptian obelisks, built circa 3500 BCE, being used as sundials, or as a minimum to divide the day into morning and afternoon. I would be most grateful if someone could provide a citation for this. When were obelisks first used for sundials? (The earliest Egyptian shadow clocks are dated circa 1500 BCE.) Gordon Gordon Uber [EMAIL PROTECTED] San Diego, California USA Webmaster: Clocks and Time: http://www.ubr.com/clocks -
Re: Latin text
The following page has Chapter 10 of Vitruvius's _De Architectura_, which includes material on Ctesibius's water clocks. The book may also have material on sundials. The site includes the entire work, and languages include Latin and English. http://www.ukans.edu/history/index/europe/ancient_rome/L/Roman/Texts/Vitruvius/10*.html Gordon At 00:43 6/10/03 +0200, Mario Arnaldi wrote: I would appreciate it if anyone could provide me with copies of (or accessible references to) Latin texts relating to the method(s) used in Ancient Rome to tell the time. (Off list for anything lengthy please). Many thanks. Fred Sawyer There are many e-text in Internet about ancient and medieval texts dedicate to this essay; you may find many links in my page http://digilander.libero.it/McArdal/Project/Link%20E-Books.htmhttp://digilander.libero.it/McArdal/Project/Link%20E-Books.htm good luck Mario Mario Arnaldi V.le Leonardo, 82 I-48020 LIDO ADRIANO - Ravenna Lat. 44° 25' N - Lon. 12° 12' E Italy E-Mail: mailto:[EMAIL PROTECTED][EMAIL PROTECTED] Web Site: http://digilander.iol.it/McArdalhttp://digilander.iol.it/McArdal Shop: http://web.tiscalinet.it/McArdalhttp://web.tiscalinet.it/McArdal --- Gordon Uber [EMAIL PROTECTED] San Diego, California USA Webmaster: Clocks and Time: http://www.ubr.com/clocks -
Re: Using a Dipleidscope
Go to the USNO site and get the time for the solar transit. It accepts cities or latitude and longitude. http://aa.usno.navy.mil/data/docs/RS_OneDay.html Today it's 11:55 AM. Gordon At 11:16 3/23/03 -0800, Brooke Clarke wrote: Hello: Can someone tell me the California (PST) time when the Sun is South for the next few days. I'm at 123:09:50.548 W, 39:11:24.692 N. Maybe the Dipleidscope can be used as a reflecting ceiling dial. Brooke Clarke - Gordon Uber [EMAIL PROTECTED] San Diego, California USA Webmaster: Clocks and Time: http://www.ubr.com/clocks -
Re: Aries and the rest
Astrology (and religion) not only affected the development of calendars, but they stimulated the advance of horology generally. Egyptian and Chinese water clocks are examples. Chinese water clocks were used determining astrologically optimal times for conception. Babylonian astronomy and timekeeping were advanced in order to predict eclipses as omens. According to a biographer, King Alfred the Great in the tenth century had candle clocks made so that he could apportion his time at night between religious and secular activities. Timekeeping was advanced in the Middle Ages to schedule monastic life and to announce times for prayer. Gordon Uber San Diego, USA At 02:31 PM 12/1/02 +0100, fer j. de vries wrote: Hello Anselmo, I agree with your argument superstition of astrology, but remember that the zodiacal calendar was very important in the past and not only by astrologers but in all kind of science. -
Obelisk as earliest sun clock?
Someone wrote me that Egyptian obelisks were used as sundials prior to Egyptian shadow clocks (shadow of a horizontal edge) of about 1500 BC. I was unaware of this and am skeptical. Obelisks have been found of earlier date, but were they used for timekeeping? If someone would provide an example, location and date it would be greatly appreciated. Citations to literature or Web? Discussion welcome. Gordon Uber -
Re: Sundial photo shoot
Bare filament lamps such as the one in your Maglite work well. For more light consider bare automobile quartz halogen headlight replacement bulbs (12 volt, 50 or 100 watt) and other 120 volt bare quartz halogen bulbs (without multi-mirror reflectors). These bulbs are hot and can explode, so putting them in a tin can with a hole for the light output and ventilating holes at the bottom and top would be safer. A 35mm slide projector is probably the easiest and safest. Gordon At 04:21 PM 7/7/02 -0400, J. Tallman wrote: Hello All, I am taking some documentary photographs of a new sundial concept and I need a little help. I recall reading several postings in the past that referred to using a point light source to simulate the sun. This would be very helpful in simulating conditions such as solstice and equinox declination, as well as any desired time of day. Accomplishing these various conditions outdoors is proving very difficult (and hot!), so I would like to set up an indoor photo shoot with a common backdrop. This way I hope to create the ideal times and declinations for my instruction sheets. Does anyone have any suggestions for a good point light source to use? I have tried several flashlights and lightbulbs and I keep getting fuzzy shadows. The best point of light I have found so far is a mini MagLight flashlight with the reflector assembly removed...but it is not as bright as I would like. Any ideas? Jim Tallman mailto:[EMAIL PROTECTED]Artisan Industrials Gordon Uber [EMAIL PROTECTED] San Diego, California USA Webmaster: Clocks and Time: http://www.ubr.com/clocks -
RE: Time Museum Auction
It may that Part 2 would have been on sundials; apparently it was never published. I don't recall seeing that many sundials at the Time Museum. At present, I am more interested in the plain sights of the large astronomical instruments with nontelescopic sights which were built by Tycho Brahe and Johannes Hevelius. The sights were remarkably good, with reproducibility as good as 10 arc seconds (Hevelius), although overall instrumental accuracy for stars was more like 20 to 60 arc seconds. The position of the sun was measured by centering the edges of a pinhole-projected solar image on four slits, in the event someone wishes to try the method on a sundial. Over this last year I have been studying about water clocks, starting with Part 3, and going on to a great many of the cited works. There is also some additional modern research on the subject, primarily concerning hydraulics. I published a brief list of these newer articles in the NAWCC Horological Science Chapter Newsletter and can send it to anyone interested. Best wishes, Gordon Gordon Uber [EMAIL PROTECTED] San Diego, California USA Webmaster: Clocks and Time: http://www.ubr.com/clocks -
Re: Time Museum Auction
The Time Museum Catalog by Anthony Turner: Volume 1, Part 1 Astrolabes, and Part 3 Water-Clocks, Sand-Glasses and Fire Clocks have been published, are out of print, and are available from used book dealers. Part 3 has the best English-language survey of water clocks (about 70 pages) that I have found; it has an extensive bibliography of supporting literature. I do not know about Part 2. I suspect that further volumes will not be published now that the museum is closed. There are also Time Museum volumes published on pocket watches and chronometers. Gordon At 02:57 PM 6/16/02 +0200, you wrote: I do own a copy of the marvelous Western Astrolabes book published by the Time Museum. I wonder whether other books of the series have been published or prepared (and if they will be published eventually?), e.g. the one planned since years about sundials? The plan supposedly was to publish a whole series as a museum catalogue. Any info appreciated! Best regards, Thierry vs 50.5N 4.3E Gordon Uber [EMAIL PROTECTED] San Diego, California USA Webmaster: Clocks and Time: http://www.ubr.com/clocks -
Re: Penumbra Ratio
The width of the penumbra on a surface is the distance from the style to the surface times the angular diameter of the sun in radians (about 1/107) divided by the cosine of the angle between the normal (perpendicular) to the surface and the sun's ray. So basically you are correct, although 1/107 would be a better value. The value varies by about +/- 2% during the year due to the elliptical orbit of the earth. For the year 1999 the following web page gives a mean solar diameter of 1923 arc seconds, corresponding to 1/107.3 radians = 0.009323 radians. The maximum is 1955 arc seconds, and the minimum is 1891 arc seconds. Angular diameters from http://www.astrosurf.com/taf/dim-ogg-neg/don-sole-eng.htm Gordon At 06:18 AM 6/15/02 -0700, you wrote: Hello All Does anybody remember the exact ratio or multiplication factor that will determine the width of the a shadow's edge penumbra if you know the distance from the style to the penumbra's image? Isn't the penumbra's with about 1/100th the projection distance? And couldn't this ratio be viewed in graphic or tabular form? I ask because I'd like to be able to calculate the theoretical penumbra width at different points along the Kitt Peak Sundial perimeter timelines. John John L. Carmichael Jr. Sundial Sculptures 925 E. Foothills Dr. Tucson Arizona 85718 USA Tel: 520-696-1709 Email: [EMAIL PROTECTED] Website: http://www.sundialsculptures.com - Gordon Uber [EMAIL PROTECTED] San Diego, California USA Webmaster: Clocks and Time: http://www.ubr.com/clocks -
RE: Why the clock rotates clockwise?
Earlier water clocks (those at Karnak and Edfu in Egypt, for example) had scales of twelve hours. Thus, one had sundials and night clocks, both with twelve-hour dials. With twelve hours each for the day and night, it would seem reasonable to have a twelve-hour dial on a mechanical clock. Some later water clocks, such as the anaphoric clock, did have 24-hour dials, corresponding to the rotation of the constellations. Several European tower clocks, often astronomical, have 24-hour dials. Gordon At 04:48 PM 6/14/02 +0100, you wrote: But I'll ask a subsidiary question If the above IS correct, why did the clockmakers make their clocks go round twice in a day, the shadow didn't. Mike Shaw mailto:[EMAIL PROTECTED] http://homepage.ntlworld.com/jmikeshaw/ N 53º 21' 24 W 03º 01' 47 Wirral, UK. Gordon Uber [EMAIL PROTECTED] San Diego, California USA Webmaster: Clocks and Time: http://www.ubr.com/clocks -
Re: About the equation of center
Jean Meeus's Astronomical Algorithms gives five abbreviated coefficients for terms up to sin 5M. He references Annales de l'Observatoire de Paris, Vol. I, pages 202-204, and only says that it is derived from a series expansion. The abbreviated coefficients are 2e - (e^3}/4 + (5/96)e^5 (5/4)e^2 - (11/24)e^4 (13/12)e^3 - (43/64)e^5 (103/96)e^4 (1097/960)e^5 I hope that the more-complete coefficients will give you additional insight. Good luck with your derivation. Gordon At 05:25 PM 4/6/02 +0200, Anselmo Pérez Serrada wrote: Hi dialists, Maybe this is an off-topic, but I found it in some gnomonics books and I'd like to know more about it: It is well known that due to Kepler's Second Law the Earth (and any satellite) does not follow a circular uniform movement but an elliptical non-uniform one. So the longitude of the Earth across the ecliptic is not exactly proportional to time: the difference (True Longitude minus Mean Longitude) is called equation of center 'c' and can be derived either solving Kepler's equation ( M = E - e*sin(E) ) or using an approximate formula, something like c = (2e- 1/4*e^3)*sin(M) + 5/4*sin(2*M) + 13/12*e^3*sin(3*M)+ ... where M, the mean anomaly, is the fraction of area swept by the Earth and e is the eccentricity of the orbit (Yes, it's pre-copernican, but it works!). OK, but which is the general expression of this formula (for the n-th term) and where does it come from? Is it a Fourier series or a Taylor series? I've tried both and wasn't able to reach to any result like this. Could anyone point me at some website where this series is derived? Anselmo Perez Serrada Gordon Uber [EMAIL PROTECTED] San Diego, California USA Webmaster: Clocks and Time: http://www.ubr.com/clocks -
Re: Precise Time
For a visual display of time, one source is http://www.time.gov, official NIST/USNO time to within 0.3 second. For automatically synchronizing my PC's time I use the YATS32 (Yet Another TIme Synchronizer) software from Dillobits Software http://www.dillobits.com which allows me to select Internet time sources. I use UCSD, ntp.ucsd.edu, which is ten miles away, with a backup source of NIST in Boulder, CO, time-A.timefreq.bldrdoc.gov. There are many PC time synchronization programs available. Gordon At 02:24 PM 3/7/02 -0500, J.Tallman wrote: Hello All, Where are the best current places online to get the precise time? The site I used to use does not seem to work anymore. Does anyone have any favorites? Jim Tallman Sr. Designer FX Studios 513.829.1888 Gordon Uber [EMAIL PROTECTED] San Diego, California USA Webmaster: Clocks and Time: http://www.ubr.com/clocks -
Re: Research Query
The North Star (Polaris) is 0.73 degrees from the true north celestial pole. I would think that sighting on Polaris would be good enough for aligning most sundials. For those on the Sundial List, if greater accuracy were desired: 1. Take the average of two sightings 12 hours apart (when the nights are long, in autumn or winter), or 2. With a star chart, ephemeris or planetarium software as a guide, take a reading when Polaris is due east or west of the pole to get the exact elevation of the gnomon. Take a reading when Polaris is due North or South of the pole to get the proper azimuth. To sight to this accuracy without an optical telescope one might try open sights such as those used by the astronomer Tycho Brahe in the 16th century. They can be precise to better than a sixtieth of a degree. Gordon Uber At 05:23 PM 2/13/02 -0500, you wrote: Hello, I am checking the facts in a garden article to be published soon, and our writer says that in the Northern Hemisphere, you can find the correct gnomon angle for your latitude by aiming the gnomon at the North Star. I know you must align it with the earth's North/South axis, but is simply aiming for the North Star enough to make the dial accurate at your latitude? Thank you so much for any clarification you can provide. Amanda -- Gordon Uber [EMAIL PROTECTED] San Diego, California USA Webmaster: Clocks and Time: http://www.ubr.com/clocks
Re: Ceiling Sundials: Mirror Placement
More information on mercury liquid mirror telescopes. Mercury mirror with Mylar film overlay http://www.abc.net.au/science/k2/moments/s64751.htm On one web page automobile motor oil was suggested in lieu of mercury. I have not been able to find the overlay liquid used by the Canadian University Laval in Quebec; it is quite possible that none is used, since they discuss skimming the surface to remove debris, at least on their gallium-indium amalgam mirror. I would suggest emailing the project for details. Details on mercury and effect of its oxide in reducing evaporation http://www.astro.ubc.ca/LMT/lm/index.html Other projects http://vela.astro.ulg.ac.be/themes/telins/lmt/links_e.html Bibliography on liquid mirror telescopes http://vela.astro.ulg.ac.be/themes/telins/lmt/bibliography.html Gordon At 10:55 PM 1/5/02 -0800, Edley McKnight wrote: Hi Gordon and mirror folk, I just thought that someone might know the oil they use to cover the mercury with so that it could be experimented with in the ceiling sundial situation in order to have a safer flat, level mirror. Gordon Uber [EMAIL PROTECTED] San Diego, California USA Webmaster: Clocks and Time: http://www.ubr.com/clocks
Re: Ceiling Sundials: Mirror Placement
Experiments with rotating mercury mirrors go back many decades. It takes a very constant speed drive to keep the focal length constant. The casting of large glass telescope mirror blanks at the University of Arizona includes rotating the oven so that the molten glass acquires a parabolic shape. Several large telescopes have been floated on mercury, for example, the 100-inch Hooker reflector on Mount Wilson, CA, and the 250-ton Dunn solar tower telescope on Sacramento Peak, NM. http://www.sunspot.noao.edu/DSTWWW/vttpr.html Gordon At 04:57 PM 1/5/02 -0800, Edley McKnight wrote: Hi John and all, John wrote: In an astronomy paper I read last year from an observatory in the southern hemisphere there was an article on a large parabolic mercury mirror obtained by rotation. The key points in the article were the need to prevent fumes from the mercury, damp vibration, prevent oxidation and eliminate the meniscus at the edges. They had found a synthetic oil or oil/polymer mix that damped the vibration, sealed the surface, with the mercury and the enclosure had no meniscus and prevented oxidation. Something like this, further sealed to prevent dust, would allow the mercury surface itself to be used as the mirror. ( I'm assuming from it's use as an astronomical mirror that the refractive effects of the liquid are minimal ) Edley McKnight [43.126N 123.357W] Gordon Uber [EMAIL PROTECTED] San Diego, California USA Webmaster: Clocks and Time: http://www.ubr.com/clocks
Arabic numerals
See http://www.scit.wlv.ac.uk/~cm1993/maths/mm2217/countsys.htm for discussion of Hindu-Arabic numbers and their dissemination in the West. Gordon At 10:44 AM 5/7/01 -0300, Steve Lelievre wrote: This is off-topic, but why are they called Arabic numerals? Presumably because the system of positional significance is Arabic in origin? Also, real Arabic digits look nothing like the digits in the West (see attached for 0 to 9, Arabic style). Why and when did the differences arise? Steve Gordon Uber [EMAIL PROTECTED] San Diego, California USA Webmaster: Clocks and Time: http://www.ubr.com/clocks
Re: ??? Roman numerals
Various explanations for the use of are given in my FAQ http://www.ubr.com/clocks/faq/.html Gordon Gordon Uber [EMAIL PROTECTED] San Diego, California USA Webmaster: Clocks and Time: http://www.ubr.com/clocks
Re: Time Zones
Your U.S. Time Zone designations are correct, but the boundaries are determined politically, not strictly by latitude, and are subject to change. For example, time in Indiana is determined by county, and a redetermination was recently considered. However, I would think (probably too optimistically) that most Americans know which time zone they are in. Daylight Saving Time is another complication, I think determined by each state. Some in California are now proposing a Double Daylight Saving Time due to the current energy crisis. Concerning Indiana see http://www.abcnews.go.com/wire/US/reuters20010319_3536.html Link to U.S. Code for Time Zone boundaries: http://www.bldrdoc.gov/timefreq/general/history.htm Gordon At 04:35 AM 3/27/01 -0500, you wrote: Dear All, Can anyone clarify American and European time zones for me? I am trying to write instructions for setting up a dial which can be used in any location. Gordon Uber [EMAIL PROTECTED] San Diego, California USA Webmaster: Clocks and Time: http://www.ubr.com/clocks
Re: Time Zones
shortly after the French Revolution. If we wish a zoneless time then let's continue to use UTC, successor to GMT, with its bases 24 and 60. These have been around a lot longer than the Swatch. Gordon At 11:58 PM 3/28/01 +0100, you wrote: Hi All I just wondered what members in the group think of the latest zoneless time concept, Internet Time where the day is broken up into beats eliminating the need for geographical based time zones. Is it seen as helping to make ours one world or as cynical commercial exploitation? see http://www.swatch.com/fs_index.phphttp://www.swatch.com/fs_index.php Gordon Uber [EMAIL PROTECTED] San Diego, California USA Webmaster: Clocks and Time: http://www.ubr.com/clocks
Re: Commercial Offerings
I have no objection to limited announcements on the Sundial List, but I would be unhappy if the number of commercial posts exceeded the number for discussion posts. Where possible, commercial emails should be brief and refer to any web sites containing more extensive information. Gordon Gordon Uber [EMAIL PROTECTED] San Diego, California USA Webmaster: Clocks and Time: http://www.ubr.com/clocks
Re: time in austria in 1803
corrections are added or subtracted to obtain mean solar (or in reverse, sundial) time. I am guessing that most church clocks in 1803 were corrected to local apparent (sundial) time using a nearby sundial, perhaps daily or weekly. I would appreciate having other comments posted to Sundials (or at least to me). Gordon We are doing a historical research. In an important document we find a time indication in Matterdorf (then on the Estates of the Count Eszterhazy in old Hungary, named Nagymarton, today: Mattersburg in Burgenland, near Eisenstadt, in Austria): on Saturday, June 18, 1803, 5 minutes before the bell finished ringing 9 p.m... Can somebody tell me, how were church clocks calibrated at that place and time, and what does it mean end of ringing the bell. Was at this time, ~ 1 h after sunset, an Ave Maria ringing, which lasted a several minutes ? Was there in Austria/Hungary in 1803 a church, state or local(of the Count ?) regulation how to set public clocks ? It was surely not meant to be apparent (=true) solar time, as it is not conceivable that the clock was set exactly at that date to show 12 at true noon. It was surely not meant to be modern mean time, as this was introduced only later (in the first third of the 19 th cent.e.g. Paris in 1816, Zurich 1832 (Ginzel III). When exactly in Austria/Hungary ?). It was surely a kind of mean time. But at what date was that mean time set to be the local true time? Perhaps at Nov. 1-3 (when modern Equation of Time was maximal), as the French did, and they used the French Equation de l'Horloge (see in the old French almanacs Conaissance des Temps of the late 18 th century)? This runs from 0-31 min this is the old Equation of Days Nights of Ptolemy in his Handy Tables - 0 min on Nov 1-3, 31 min on February 11) which had to be added to true(=sundial) time, to give mean (=clock) time ? Pls. advise! Thanks. Yaaqov L o e w i n g e r mail : P.O.B. 16 229 ; 61 161 Tel Aviv / Israel tel. : 972-3- 604 61 79; ++ 523 98 33 fax : 972-3- 546 90 76 e-mail : [EMAIL PROTECTED] Gordon Uber [EMAIL PROTECTED] San Diego, California USA Webmaster: Clocks and Time: http://www.ubr.com/clocks
Re: Rainbow geometry
The geometry of rainbows is determined by reflection and refraction within spherical water droplets. This is explained in many optics and related books. See The Nature of Light and Colour in the Open Air by Marcel Gilles Jozef Minnaert (Paperback - December 1948) For a Web simulation, geometry and optical ray tracing see http://webphysics.ph.msstate.edu/jc/library/24-8b/ Gordon At 09:50 AM 1/11/01 -0500, you wrote: Hello All, What a fascinating observation on the practical aspects of a rainbow...thanks for the commentary John. I have always been interested in rainbows, ever since my third grade teacher took the whole class out trudging through the fields after a rainstorm, looking for the pot at the end of the rainbow. We never found it...maybe the rainbow was the pot that day. Does anyone know the determining factor for the radius of a rainbow? Jim Tallman Sr. Designer FX Studios Gordon Uber [EMAIL PROTECTED] San Diego, California USA Webmaster: Clocks and Time: http://www.ubr.com/clocks
Re: sunspots
I think that the SOHO images are updated at least once a day. The latest sunspot image was taken at 10:16 UT today. The satellite is in a zero-gravity region between the earth and the sun, so I would think that it is always on our side of the sun, although I don't know for certain. The sun's rotation period is a function of latitude, 25 days at the equator, 33 days at 75 degrees (Skilling and Richardson, 1947). SOHO images are at http://sohowww.nascom.nasa.gov/data/realtime-update.html Gordon At 07:14 AM 1/3/01 -0700, you wrote: Hello all: I just looked at the SOHO solar satellite photos of the sunspots and noticed that the spots were different from the ones I saw on Christmas morning. Could it be that SOHO was on the opposite side of the sun when the picture was taken? Or maybe the sun's rotation since Christmass brought the sun's farside into view. If an earthboud observer wants to see both sides of the sun, how long will he have to wait between observations until the sun rotates 180 degrees? What is the rotation rate of the sun? John Carmichael Tucson Arizona Gordon Uber [EMAIL PROTECTED] San Diego, California USA Webmaster: Clocks and Time: http://www.ubr.com/clocks
Re: Cast Away
I suspect that the analemma, being familiar to the public on globes, sundials, etc., was used solely for that reason, call it artistic license. Sun position lines (corresponding to the latitude dimension of an analemma) were marked on the floors of some cathedrals. See J. L. Heilbron's 1999 book The sun in the church: cathedrals as solar observatories. Prior to the availability of accurate clocks, the Equation of Time was determined by measuring the longitude of the sun. This was done by determining the position of the sun relative to the stars. Since the sun was observable only during the day, and the stars only at night, a mutually observable body was used to facilitate the measurement: the moon by the ancient astronomers and Venus by Tycho Brahe. The maximum 16-minute value of the Equation of Time corresponds to about 4 degrees of arc, so that observing instruments should be much more accurate than this. Gordon Gordon Uber [EMAIL PROTECTED] San Diego, California USA Webmaster: Clocks and Time: http://www.ubr.com/clocks
Re: Cast Away
He could mark the vertical motion due to changes in declination, marking off the days. Then he could label the two solstices as June 21 and December 21 and number the days of the months between based on these. I don't think that he could easily determine the equation of time without a watch (although the ancients of course did), nor do I think that it would matter much to him. Gordon At 07:59 PM 1/1/01 -0500, [EMAIL PROTECTED] wrote: I saw Cast Away last week, and had a question about sudials and the movie. After Tom Hanks has spent several years on a desolate island, he constructs an impressive analemma from a thin beam of light that enters his cave, complete with days of the months. This would not be hard, if he had a working watch, but I don't think he did. So, my question is, is this just Hollywood chicanery, or is it really a possible thing to do? Bill G. (I need to know, in case my plane goes down in the south Pacific some day). Gordon Uber [EMAIL PROTECTED] San Diego, California USA Webmaster: Clocks and Time: http://www.ubr.com/clocks
Re: Determining hour-angle from azimuth
From Jean Meeus's Astronomical Algorithms, 1951, p. 89: tan H = sin A / (cos A * cos f + tan h * cos f) where H is hour angle, A is azimuth, f is latitude and h is altitude, and H is obtained via the arctangent. He further remarks, p. 90, that the quadrant of the arctangent is unknown and that it can be obtained by using the ATN2 function, if available, or by the techniques in his Chapter 1 concerning The Correct Quadrant. I hope that this is helpful. Gordon At 02:54 PM 12/12/00 -0400, Steve Lelievre wrote: I'm trying to convert an azimuth value into an hour-angle, and would appreciate some help with the formula and with my algebra. Using dcl=declination, lat=latitude, azi=azimuth,ha=hour-angle, I started with a standard formula for azimuth given hour-angle: tan(azi) = sin(ha)/(sin(lat)*cos(ha) + tan(dcl)*cos(lat)) After multiplying out and rearranging, I got: sin(lat)*tan(azi)*cos(ha) - sin(ha) = -tan(azi)*tan(dcl)*cos(lat) Substituting into a standard fromula from my old notes from school, this solves as: ha = arctan(-1 / sin(lat)*tan(azi)) + - arccos( -tan(azi)*tan(dcl)*cos(lat) / sqrt( sin(lat)^2 * tan(azi)^2 +1 )) where + - means plus or minus Questions: Is this the correct solution? If so, how should I interpret the plus or minus element of the solution. Surely for any given azimuth-latitude-declination there is only one possible hour-angle, not the two implied by the plus or minus option? Many thanks, Steve Gordon Uber [EMAIL PROTECTED] San Diego, California USA Webmaster: Clocks and Time: http://www.ubr.com/clocks
Needed: history of equation of time
recommend a reference (preferably in English) on the subject? I understand that John Flamsteed and Christiaan Huygens published tables of it in 1666 and 1662, respectively. If anyone has copies of these tables, the tables (or citations to them) would be greatly appreciated. So far I have located G. Toomer's translation of Ptolemy's Almagest, which has a section on it, as does Neugebauer's History of Ancient Mathematical Astronomy. I am following up on some articles in the NAWCC Bulletin. Any help would be greatly appreciated. Gordon Gordon Uber [EMAIL PROTECTED] San Diego, California USA Webmaster: Clocks and Time: http://www.ubr.com/clocks
RE: Length of the year
years had been discovered by Babylonian astronomers prior to 502 BC. This led Hipparchus to determine precession circa 150 BC. The length of the tropical year was determined with a gnomen between successive solar solstices. The length of the sidereal year was determined from successive heliacal risings. From Time in History by G. J. Whitrow. Hipparchus found the interval between successive equinoxes was 365.25 days - 1/300 = 365.2497, in excess by 0.0044 days or about 6 minutes. Hipparchus had found values for the tropical year and for the sidereal year by comparing his observations of the angular separations of stars (Spica and Regulus) from equinoctial or solstitial points with those of Timocharis and Aristyllos some 160 years before. The stars had shifted 2 degrees eastward. Precession was between 1 degree in 100 years and 1 degree in 78 years. The sidereal year was 365.2569 days, about 0.78 minutes too long. He may have had sextants, quadrants, equatorial armillae, armillary spheres and/or planispheric astrolabes. (Further details of interest but omitted.) From Early Astronomy from Babylonia to Copernicus by W. M. O'Neil. Gordon Gordon Uber [EMAIL PROTECTED] San Diego, California USA Webmaster: Clocks and Time: http://www.ubr.com/clocks
Re: Off topic, but...
It is a great story, which I still enjoy, but I understand that it arose concerning different student at Washington University in St. Louis, Missouri--not Niels Bohr in Copenhagen. Gordon Gordon Uber [EMAIL PROTECTED] San Diego, California USA Webmaster: Clocks and Time: http://www.ubr.com/clocks
Re: IIII at IV
I don't consider the use of either or IV an error but rather a choice to use a specific representation. Various reasons have been given, including unsubstantiated anecdotes, for the preference of vs. IV on clock dials. On clock dials preference is often given to the aesthetics of greater symmetry when is used. There is also a tradition of using . I would dispute that IV is more correct than since both are valid and understandable representations of the number four. I agree that modern usage favors the shorter IV--except on clock dials. For further discussion of this topic see my Web site http://www.ubr.com/clocks/faq/.html To shed further light on usage, the only Latin text I have at the moment is Frontinus's DE AQVIS VRBIS ROMAE, written about 97 AD. It contains such representations as , X and V, but also XXIX and XIV. The manuscript dates from about 1200 or 1300 AD. Because a few of the numbers (not necessarily relating to vs. IV) are different in different editions, it is difficult to be certain which of these were in the original and which were introduced by various scribes. But I think that this supports the early usage of (and perhaps also IV) in Rome circa 100 AD. Those familiar with early Roman dials may wish to comment on the usage in these. Gordon At 08:50 AM 7/21/00 +0100, [EMAIL PROTECTED] wrote: I've been following the discourse on 'Nought at noon' and this has reminded me of an anomoly which has puzzled me for years. In my school technology course we undertake a project on time and so we get a lot of clocks and sundials which the students design and make. A question I am often asked is why do English clocks with Roman numerals have (instead of IV) at the '4' position and most Continental and American clocks appear to have the correct IV? Was this an error on the part of some early clockmaker which was continued eventually to become a tradition or is there some other reason? Gordon Uber [EMAIL PROTECTED] San Diego, California USA Webmaster: Clocks and Time: http://www.ubr.com/clocks
Re: A Comment and a Question
See Astronomical Algorithms by Jean Meeus, pp 135-6. It is recommended for astronomical calculations. The Astronomical Almanac probably has values also. The mean obliquity is (defined by the International Astronomical Union): 23 deg 26'21.448 - 46.8150 T - 0.00059 T^2 + 0.001 813 T^3 where T is in Julian centuries from J2000.0. This is the angle between the ecliptic and the mean equator. The angle with the true equator, the true obliquity, is also given, differing by the nutation in obliquity. In the example given they differ by 9. Gordon At 10:26 AM 4/12/00 -0400, Robert Terwilliger wrote: Question: Is there a source, or value, for the exact inclination of the earth's axis? I understand it is decreasing slightly. The last value I used was 23.4385 degrees. I cannot remember where I got it. Bob Gordon Uber [EMAIL PROTECTED] San Diego, California USA Webmaster: Clocks and Time: http://www.ubr.com/clocks
Diffraction: Poisson's spot
In 1818 Fresnel entered a competition sponsored by the French Academy. His paper on the theory of diffraction ultimately won first prize and the title Memoire Courronne, but not before it had provided the basis for a rather interesting story. The judging committee consisted of Pierre Laplace, Jean B. Biot, Simeon D. Poisson, Dominique F. Arago and Joseph L Gay-Lussac, a formidable group indeed. Poisson, who was an ardent protagonist against the wave description of light, deduced a remarkable and seeming untenable conclusion from Fresnel's theory. He showed that a bright spot would be visible at the center of the shadow of a circular opaque obstacle; a result which he felt proved the absurdity of Fresnel's treatment This surprising prediction, fashioned by Poisson as the death blow to the wave theory, was almost immediately verified by Arago: the spot actually existed. Amusingly enough, Poisson's spot, as it is now called, had been observed many years earlier (1723) by Maraldi but this work had long gone unnoticed. Gordon Uber [EMAIL PROTECTED] San Diego, California USA Webmaster: Clocks and Time: http://www.ubr.com/clocks
Re: Zero point on the Analemma Answer
graphs of the EOT for successive millennia from about 3000 BC to 4000 AD. It also has the complete equations for two methods of computing the EOT. It is a great book of algorithms for solar, lunar and planetary positions, among other things. Gordon Gordon Uber [EMAIL PROTECTED] San Diego, California USA Webmaster: Clocks and Time: http://www.ubr.com/clocks
Re: MDF - Materials for Sundial Making
Here are a few Web sites with information on MDF and/or HDF. Georgia Pacific http://www.gp.com/build/products/ebspec.html#mdf Exim Corp. http://www.eximcorp.org/Products/Fiberboardmoisture/MRMDFProperties/mrmdfpro perties.html US Forest Products Lab Publications (search their Handbook for MDF) http://www.fpl.fs.fed.us/pubs.htm Gordon At 03:09 AM 3/5/00 +, Tony Moss wrote: Fellow Shadow Watchers, An old school friend in Vancouver confirms that he has been using the material 'MDF' (Medium Density Fibreboard) and calling it by that name for many years. Surely it must be the same in the USA? - is it? Tony Moss P.S. I'm still anxious to encounter 'HDF' i.e *HIGH* Density Fibreboard. THAT would be MAGIC! Gordon Uber [EMAIL PROTECTED] San Diego, California USA Webmaster: Clocks and Time: http://www.ubr.com/clocks
Re: Metric v's Imperial.
Let's face it: The Babylonians got it right when they developed the base-60 system. It was applied to the sixth of a circle (one sixtieth of this being a degree) and the hour, of which we still use the first and second minutes. Third minutes (sixtieths of second minutes) are not in common use, although I would note that the third minute of an hour is the period of U.S. power main standard 60 Hz alternating current. Coincidence? The arc minute is so convenient for expressing human visual acuity because the value of the latter is coincidentally close to 1 arc minute. For practical calculations at small angles arc minutes and arc seconds are best converted to radians, the arc second being approximately 5 microradians, the arc minute about 17 milliradians. And, of course, the angular diameter of the sun is approximately 10 milliradians. Gordon At 10:55 AM 2/15/00 -0700, Jim_Cobb wrote: The radian is a natural measure of angle, but I would suppose everyone subscribing to this list uses degrees, minutes, and seconds. For example, I haven't seen any of the recent discussion about human visual acuity conducted in terms of radians. Gordon Uber [EMAIL PROTECTED] San Diego, California USA Webmaster: Clocks and Time: http://www.ubr.com/clocks
Re: Metric - What is the 'legal' USA situation ?
U.S. Federal contracts require metric units (but usually not standard metric sizes) . The U.S. populace still thinks in English customary units. For example, highway construction is specified in metric units; highway speeds are in customary units. U.S. customary units have long been legally defined in terms of metric units. For example, the inch is now defined as 25.4 mm, formerly 100/3937 metre. The European Union has deferred its metric-only labeling requirement until 31 December 2009. http://www.ansi.org/public/news/1998feb/eulbl_11.html See the following for a 1998 discussion of metric fasteners: http://www.manufacturing.net/magazine/id/archives/1998/ind0301.98/fastners/c utting.htm List of historical definitions of the metre http://lamar.colostate.edu/~hillger/meter.htm A news article in Mother Jones Magazine on the U.S. Metric Program office http://bsd.mojones.com/mother_jones/JF99/zengerle.html U. S. Code on metric units http://www4.law.cornell.edu/uscode/15/ch6.html#PC6 U.S. Code on time, weights and measures http://www4.law.cornell.edu/uscode/15/ch6.html NIST Metric Links http://ts.nist.gov/ts/htdocs/200/202/mpo_reso.htm U. S. General Services Administration's Metric Design Guide (Interesting details of hard and soft conversion) http://www.gsa.gov/pbs/pc/tc_files/stds/metricgd.pdf Gordon At 03:43 PM 2/13/00 +, Mr. D. Hunt wrote: What exactly is the current situation, in the UNITED STATES, re. 'metric' measurements ? - as I was led to believe it is the LEGAL standard there ! Gordon Uber [EMAIL PROTECTED] San Diego, California USA Webmaster: Clocks and Time: http://www.ubr.com/clocks
Re: optical resolution problem
The minimum would be one arc minute for stroke width and a five arc minute height for characters if they are to be legible. This is the basis for 20/20 vision (resolution or visual acuity) on eye charts. I would think that you would want to at least double this. One can detect and determine the location of a shadow that is narrower than this. I seem to recollect that power lines can be detected against the sky when their width is perhaps five or ten arc seconds. Gordon At 06:55 PM 2/10/00 -0700, John Carmichael wrote: Good dialing question Ross Caldwell! (We might need an optomologist for this one.) John Carmichael You write: Do you know of any kind of formula to estimate the proper proportions for seeing high or distant dial lines, letters etc. clearly? I suspect architects, engineers and advertisers (billboards) must have some way of knowing what will be clear to a given eye at a given distance. Ross Caldwell [EMAIL PROTECTED] 119 48 11W 36 46 14N Fresno, CA USA Gordon Uber [EMAIL PROTECTED] San Diego, California USA Webmaster: Clocks and Time: http://www.ubr.com/clocks
Re: Tycho Brahe
Author: Brahe, Tycho, 1546-1601 Title: Tycho Brahe's description of his instruments and scientific work, as given in Astronomiae instauratae mechanica (Wandesburgi 1598) Translated and edited by Hans Raeder, Elis Strmgren and Bengt Strmgren Published: Kobenhavn, I Kommission hos E. Munksgaard, 1946 Also see the bibliography in Author: Thoren, Victor E Title: The Lord of Uraniborg : a biography of Tycho Brahe / Victor E. Thoren ; with contributions by John R. Christianson Published: Cambridge [England] ; New York : Cambridge University Press, 1990 Gordon At 01:43 AM 12/07/1999 , Mainsa wrote: Friends: I know there is a translation into English (1946) of the book Astronomiae Instaurate Mechanica by Tycho Brahe. Know you the complete reference of this book or other translation into Spanish, French, Italian or Portuguese? Gordon Uber [EMAIL PROTECTED] San Diego, California USA Webmaster: Clocks and Time: http://www.ubr.com/clocks
Re: Ptolemy's Almagest
Neugebauer's The Exact Sciences in Antiquity, New York, Dover Publications, 1969. This especially discusses Babylonian astronomy, with some treatment of Egyptian and Greek astronomy. Those more deeply into math may like his out-of-print three-volume mathematically-oriented treatise A history of ancient mathematical astronomy, Berlin ; New York, Springer-Verlag, 1975. Gordon Gordon Uber [EMAIL PROTECTED] San Diego, California USA Webmaster: Clocks and Time: http://www.ubr.com/clocks
Re: patents copyrights
Just a few informal observations (not legal advice). The originator of a work has automatic copyrights even without registering it, although registration (which is easy and inexpensive) does provide additional rights (recovery of court costs, usually a prerequisite to hiring a lawyer on a contingency basis). However, I question that most sundial designs are commercially valuable enough to go to court over to recover damages. Patents are different and must be both novel and applied for. A working model is (I believe) no longer necessary. I doubt that most sundial designs are commercially valuable enough to be worth applying for a patent, although it may be ego-satisfying. Given the long global history of sundials, I would think it might be difficult to prove that a patent concept was novel, unless based upon recent technology such as lasers or LCDs. The above being said, I would think it courteous to discuss the proposed use with the originator, albeit with the legal risks that this entails. Gordon At 07:31 AM 11/28/1999 , John Carmichael wrote: But who has the legal rights to the finished sundial, the author of the original article or the manufacturer? If novel, the author has copyrights to that which he published. Now I'm no lawyer, but I would assume that the original author wouldn't have published his new design if he didn't want the sundial to be built. Just because an author publishes a book, for example, does not mean that he/she grants rights to base a movie on it without royalties. Now I know that under copyright law that it's pretty much first come first served. In other words, the first person to apply for copyright or patent registration, regardless if he is the author or not, becomes the owner of the invention. If an idea is published then I do not think it to be subsequently patentable by someone else who only reads of it, and I think that there are time restrictions as to when the publisher can apply for a patent before it enters the public domain. Gordon Uber [EMAIL PROTECTED] San Diego, California USA Webmaster: Clocks and Time: http://www.ubr.com/clocks
Re: Making Metal Sundials II
http://www.techniks.com/press-n-peel.html Price there is $30 for 20 sheets. Gordon At 11:59 AM 11/22/1999 , Tony Moss wrote: Al Schoepp contributed: It sounds similar to the film described above. Tell me more. It comes in 8.5 X 11 sheets and seems to cost about $1.50 - $2.00 per sheet, depending on where you buy it. Rather than atempting to explain it following are 2 webpages, the Techniks page is the manufacturer of the film. The other site has some info on it and also sells the stuff in the UK. http://www.cibs.co.uk/etch/ Gordon Uber [EMAIL PROTECTED] San Diego, California USA Webmaster: Clocks and Time: http://www.ubr.com/clocks
Re: easy metal gnomons
Youngstown Aluminum Products (Youngstown, Ohio) http://www.yapinc.com/contact.htm has 1/4 quarter round listed under cove, extrusion #234. Gordon At 06:02 PM 11/03/1999 , John Carmichael wrote: Ron Anthony wrote: Anyone know where I could get quarter round in various sizes, say 1/4 to Gordon Uber [EMAIL PROTECTED] California, USA Reynen Uber Web Design http://www.ubr.com/reyubr/ Webmaster: Clocks and Time http://www.ubr.com/clocks/
Re: The magic which is a dial!
Tom, The International Bureau of Weights and Measures 1875-1975, NBS Special Publication 420, discusses the 1791 decision to use the length of the earth's quadrant rather than the length of the seconds pendulum for the length of the metre because gravity (and thus the pendulum length) varied over the surface of the earth. See my History page http://www.ubr.com/clocks/hist/hist.htmlhttp://www.ubr.com/clocks/hist/hi st.html for articles (by Nelson and Olsson, and by Heyl and Cook) on using the pendulum for determining gravity. Delambre and Me'chain measured the arc of the meridian between Dunkirk and Barcelona. It states that the Metre des Archives is about 0.2 mm shorter than 1 ten-millionth of the quadrant. From the Explanatory Supplement (p. 220) I see that the value for the earth's semimajor axis has changed from 6377563 meters in 1830 to 6378136 meters in 1989, about +0.009%, in those years alone. Gordon At 05:26 PM 10/16/1999 , Tom wrote: I tried to verify your statement to the effect that: We now know however that the length of the quadrant is really 0.023% larger than originally surveyed, ... and got hopelessly lost in Chapter 4 of the Explanatory Supplement (© 1992) and in Appendix X of Bowditch, 1977 Ed. Gordon Uber [EMAIL PROTECTED] Reynen Uber Web Design http://www.ubr.com/reyubr/ Webmaster: Clocks and Time http://www.ubr.com/clocks/
Re: GPS
Frank, The first GPS Week 1024 epoch rollover will occur at about midnight of 21-22 August. The rollover occurs every 1024 weeks. Date (and possibly time) may be incorrect for those GPS receivers that do not incorporate a workaround to deduce the new epoch. Before reading the pages below I had thought that navigation was unaffected. I think that recently manufactured receivers are more likely to incorporate a workaround and to be correct during and after this rollover. See http://www.2k-times.com/y2k-a118.htmhttp://www.2k-times.com/y2k-a118.htm More at http://www.laafb.af.mil/SMC/CZ/homepage/y2000/http://www.laafb.af.mil/SMC /CZ/homepage/y2000/ including a list of (primarily military) receivers that have passed compliance tests for this and the Y2K problem. If this rollover presents a potential problem to you then contact your GPS receiver manufacturer (or their Web site) regarding compliance of your specific model and version. I think that a more complete Web search will locate much more on this problem. Gordon At 11:11 AM 8/16/99 , Frank Evans wrote: My wife half-heard a piece on the radio this morning saying that GPS instruments would fail next week unless they had previously been modified to take account of some transmission changes. They would simply be unable to find a position. Sound a bit like the millennium bug. Does anyone have any information about this, please? Users were advised to contact their suppliers. I'm feeling lost already so can you help? Gordon Uber [EMAIL PROTECTED] Reynen Uber Web Design http://www.ubr.com/reyubr/ Webmaster: Clocks and Time http://www.ubr.com/clocks/
Re: Book by Mueller
Anton, I think you are looking for Astronomical Algorithms by Jean Meeus, 2nd edition, 1999, $24.95, published by Willmann-Bell, Inc., http://www.willbell.com/http://www.willbell.com. An excellent book, by the way; I recommend it. Gordon At 02:32 AM 8/4/99 , Anton Reynecke wrote: Good morning! I need some help with finding a (well-known, I'm sure) book by Mueller. The title is something like Fundamental astronomical algorithms. Gordon Uber [EMAIL PROTECTED] Reynen Uber Web Design http://www.ubr.com/reyubr/ Webmaster: Clocks and Time http://www.ubr.com/clocks/
Re: fotocopier errors
John, I'm guessing that some photocopiers may be purposely set to a slight reduction to ensure that the edges are copied. Further, I doubt that most users care whether or not the reproduction ratio is exact. For the copier in question you could have copied at a nominal 102% to reduce the error once you had measured it. Those in the graphic arts field would be more concerned with accurate reproduction ratios; for example, the cyan, magenta and yellow color printing plates have to match quite precisely. Those in the semiconductor and printed circuit board industries are extremely concerned about accuracy. They are more likely to require Bureau of Standards (now NIST) traceability. Some digital scanners and printers have a photoetched comb controlling the scanning, which I think is quite accurate. Of course, this only applies to the mechanical scanning dimension. The scale may be different for each axis, however. You might try using these. When I was printing vernier protractors on a Hewlett-Packard LaserJet printer some years ago I was impressed by its accuracy. In response to your comment about rulers, I just checked an old Westcott wooden ruler against a Ohio Forge steel tape, and they agree to within about 0.005 over 15. Gordon At 10:25 AM 7/24/99 , John Carmichael wrote: But beware! I found out a while back that most copiers will not reproduce a copy to the exact size that you program it to do. Yesterday, I showed the surprised manager of Kinko's (a respected fotocopy shop) that when we fotocopied a 16 ruler at 100 %, the copy measured 15 3/4 !!! We then checked five different machines and none of them produced same-size copies (except for a small digital copier). The manager and I wondered if the machines could be calibrated and if they are covered by the Bureau of standards? By the way, did you know that different brands of rulers measure differently!? Be careful with those. (I always use the same architectural ruler to avoid problems.) John Carmichael http://www.azstarnet.com/~pappashttp://www.azstarnet.com/~pappas Gordon Uber [EMAIL PROTECTED] Reynen Uber Web Design http://www.ubr.com/reyubr/ Webmaster: Clocks and Time http://www.ubr.com/clocks/
Re: Off topic but interesting enough to share
Tony, A moving fluid has a lower pressure due to the Bernoulli effect. This principle explains the operation of aspirators and the lift of airplanes. An example of this (I understand) is that if you blow through the hole in the center of a spool then a piece of paper placed at the end of the spool will be attracted to it. I suspect that this is what you are experiencing. Gordon At 01:12 AM 7/14/99 , Tony Moss wrote: Fellow shadow watchers, No doubt the following is well known but it came as a surprise to me. While filling a watering can with a garden hosepipe adjusted to give a powerful single jet* I have to PUSH the hose firmly into the can to overcome the reaction from the water jet BUT as soon as I dip the nozzle into the water a smaller force takes over and seems to PULL it gently down into the water. (no measurements made so purely subjective conclusions) i.e. the force reverses on entry! Why is this so? and, if I'm right, how do 'jet' boats, working on the reaction principle, function at all I wonder? * The nozzle is one of those variable things which screw back and forth around a central pin. The 'single jet' is more of a tight spray pattern really. Tony (should have paid more attention in Physics lessons) Moss Gordon Uber [EMAIL PROTECTED] Reynen Uber Web Design http://www.ubr.com/reyubr/ Webmaster: Clocks and Time http://www.ubr.com/clocks/
Re: heliograph
Frank, It may be a surveying party for the triangulation of India: a square of four corners, with three sides being sufficient for signaling between the four stations. At those distances I suspect that only the heliograph could be observed with a theodolite during the daytime. Gordon At 12:47 PM 6/23/99 , you wrote: Maybe somebody can remember more of Kipling's poem referred to earlier than I can. Or even the title. It was about India, I'm fairly sure. Part went something like: Are you there, are you there, are you there? Three sides of a ninety mile square, With a helio winking like fun in the sun, Are you there, are you there, are you there? Gordon Uber [EMAIL PROTECTED] Reynen Uber Web Design http://www.ubr.com/reyubr/ Webmaster: Clocks and Time http://www.ubr.com/clocks/
Re: Solar mean time
The following are from amazon.com, special order, estimated delivery 4-6 weeks. Most seem to have been published by various astrological presses, originally in the mid 1960s. Our local public library has several in their reference section. Time Changes in Canada and Mexico -- Doris C. Doane, 1980; Paperback $10.35 Doane's 1986-1990 World Wide Time Change Update -- Doris C. Doane, 1991, Paperback $9.35 Time Changes in the World (Except Canada, Mexico, USA) -- Doris C. Doane, 1982; Paperback $13.00 Time Changes in the U.S.A. -- Doris C. Doane, 1985, $18.00 Gordon At 07:42 AM 6/14/99 , William P Thayer wrote: The best reference for the introduction of mean solar time, and indeed for things such as railway time, local times, daylight savings time, etc. is a 2-volume work by Doris Chase Doane. I'm quite positive about her name, but don't remember the title of the work itself; she is the authority used -- hold your breath folks -- by professional astrologers, who of course need to know what variety of time they're delaing with for any given nativity. The book is not that rare, possibly reprinted, it wouldn't surprise me, and can be found or ordered thru serious astrology supply houses. Vol. I covers the United States, Vol. II the rest of the world. That is not exactly chauvinism, BTW: due to our autonomous states, early railways over large distances in longitude, etc. the history of time zones in the US is unusually complicated. Bill Thayer LacusCurtius http://www.ukans.edu/history/index/europe/ancient_rome/E/Romanhttp://www .ukans.edu/history/index/europe/ancient_rome/E/Roman Gordon Uber [EMAIL PROTECTED] Reynen Uber Web Design http://www.ubr.com/reyubr/ Webmaster: Clocks and Time http://www.ubr.com/clocks/
Re: Related mail lists
My Clocks and Time's Mailing Lists page http://www.ubr.com/clocks/maillist/maillist.htmlhttp://www.ubr.com/clock s/maillist/maillist.html has instructions for several mailing lists: Clocks Mailing List A public list owned by John C. Wyman. Clock and watch repair and technology. Clocksmiths Mailing List A private list, owned by Clarke Smith (formerly Clockers). Clock repair. NAWCC Members Forum A private members list. Participate in the operation of the NAWCC. Sundial Mailing List A public list owned by Daniel Roth. GNOMONICA Mailing List [Italian] A public list owned by Nicola Severino. Sundials. CALNDR-L Mailing List A public list for social, historical and philosophical dimensions of Calendars and Time Reckoning. Note that to subscribe to the Clocks List the corrected instructions are: AOL Subscribers Put a . (period) in the subject line in the messages below. Subscribing Send the following mail message (containing no other text) to [EMAIL PROTECTED] SUB CLOCKS your_first_name your_last_name For example, if your name is John Doe then the message would be sub clocks John Doe A confirmation message will be sent to you, and you must respond to it as directed to complete the subscription process. Gordon Gordon Uber [EMAIL PROTECTED] Reynen Uber Web Design http://www.ubr.com/reyubr/ Webmaster: Clocks and Time http://www.ubr.com/clocks/
Re: Shadow Sharpener
Roger, thank you for your post. The Shadow Sharpener being a pinhole camera, why not replace the gnomon with a pinhole? One then could center a circle on the image and determine the time from its position. My rule of thumb is that the angular resolution of a pinhole is one radian (57 degrees) divided by the diameter of the pinhole in wavelengths of light. Since the wavelength of green light is about 0.0005 mm, the resolution for a 2 mm pinhole would be about 0.0005/2.0 = 1/4000 radian or about 0.8 arcminute or 3 seconds of time. This seems consistent with your observations. To achieve this resolution the pinhole would have to be greater than 4000 * 2 mm = 8 meters from the image. Using a slit perpendicular to the direction of motion of the image would increase the brightness of the image without decreasing the time resolution. A lens, such as one from a pair of reading glasses, would provide still greater brightness. As a rough approximation, the brightness (technically the illuminance) of the sun's image relative to that of a sunlit surface is proportional to the area of the pinhole divided by the area of the sun's image. Since the angular diameter of the sun is about 1/100 of a radian, the brightnesses are about equal when the pinhole diameter is 1/100 of the distance from the pinhole to the image. Gordon At 07:52 PM 5/3/99 , Roger Bailey wrote: By observing the shape of the image of the sun, the middle and the two edges of the penumbra were easily determined to a precision better than one inch over the width of the penumbra (about 2 ft). This gives a precision equivalent to about 5 seconds per day for this size of shadow. The bisected hemispherical image would be the appropriate position for the sun as a point source with no semi-diameter correction required. Fixing the hole and screen and timing the movement of the shadow would give even more precise results for these events (but if I had a watch, why would I need a sundial). Gordon Uber [EMAIL PROTECTED] Reynen Uber Web Design http://www.ubr.com/reyubr/ Webmaster: Clocks and Time http://www.ubr.com/clocks/
Re: accurate vs. precise
John, Accurate and precise are relative terms; they are meaningful only in context. I would think that one could have a ring sundial that was precise relative to other ring dials, although not precise relative to large, finely-divided dials. I agree that in general large dials with small divisions can be read more precisely. It is surely possible to have a precise dial that is not accurate, for example one with incorrect divisions. At 08:35 AM 4/29/99 , Phil Pappas wrote: Is it possible to have an accurate sundial that is not precise? (I think so) Is it possible to have a precise sundial that is not accurate? (I think not) John Carmichael Tucson tel: 520-696-1709 website: http://www.azstarnet.com/~pappashttp://www.azstarnet.com/~pappas Gordon Uber [EMAIL PROTECTED] Reynen Uber Web Design http://www.ubr.com/reyubr/ Webmaster: Clocks and Time http://www.ubr.com/clocks/
Re: Name of sunlight recording device.
Chuck, As your description indicates, it is a sunshine recorder. I don't remember the inventor's name, which I think is associated with it. I saw a description and operating instructions in an old British Meteorological Office manual dating perhaps from 1940 to 1950. You might try suppliers of meteorological instruments, perhaps in the United Kingdom, or else dealers in antique scientific instruments. It may be that they are no longer made, having been superseded by photoelectric detectors and recorders. You could probably make your own using a glass sphere crystal ball and thermal FAX or recorder paper. Gordon At 08:46 AM 4/13/99 , Chuck O'Connell wrote: Hi Everyone, Does anybody know the name the device described below? It looks like a glass sphere held in the center of a small equatorial sundial. The image of the sun focuses to a point at some short distance away from the surface of the glass sphere. Held in place at this distance away from the glass and following the curve of the sphere is a piece of waxpaper against a dark background. When the sun shines, the waxpaper is scorched. When the sun is behind the clouds, it is not scorched. The result is a recording of the amount of sunshine seen at that location on that day. At least this is how it appears to me from a picture I have seen. Anybody have a name and possibly a source to buy one? Thanks, Chuck. Gordon Uber [EMAIL PROTECTED] Reynen Uber Web Design http://www.ubr.com/reyubr/ Webmaster: Clocks and Time http://www.ubr.com/clocks/
Re: Population and latitude.
Jim, Many large atlases have world maps showing population densities. These maps may be instructive to him and give him a rough answer. Lines of latitude passing through the major cities such as New York, Tokyo, and Mexico City would be good candidates. NASA (I think) has published a composite photo of the entire earth at night showing the lights from cities; again; it would be instructive. It has been reprinted many times; I think it has appeared in National Geographic Magazine. The search for the answer may be more interesting and educational than the final answer itself, which may be inconclusive. Gordon At 05:55 AM 3/4/99 , Jim Tallman wrote: Hello all, I wonder if any of you guys know of a reference source relating to population and latitude. What is the most populated latitude on the globe? I endeavor to answer an earnest six-year-old's simple question...Jim Tallman, Fx Studios. Gordon Uber [EMAIL PROTECTED] Reynen Uber Web Design http://www.ubr.com/reyubr/ Webmaster: Clocks and Time http://www.ubr.com/clocks/
Re: slowing rotation
John, The earth will not stop completely, at least due to tidal friction. Ignoring nonlinear effects, the tides cause an exponential decay in rotation rate, a given fraction every year. The water in an initially-stirred jar of water never stops either (in theory) for the same reasons. I yield to others for answers to your other interesting questions. Gordon At 06:56 AM 2/28/99 , Phil Pappas wrote: Hi guys, If the earth's rotation is slowing, due to lunar tidal drag, then in what year will it stop completely? Gordon Uber [EMAIL PROTECTED] Reynen Uber Web Design http://www.ubr.com/reyubr/ Webmaster: Clocks and Time http://www.ubr.com/clocks/
Re: Astronomical help
Henry, You might start with data from the U.S. National Earth Orientation Service. See the page at http://maia.usno.navy.mil/http://maia.usno.navy.mil/ This includes nutation and (UT1 - UTC). The International Earth Rotation Service is at http://hpiers.obspm.fr/http://hpiers.obspm.fr/ Gordon At 03:26 PM 1/8/99 , [EMAIL PROTECTED] wrote: I would like to find out the speed of rotation of the Earth. I am currently repairing a geosynchronous clock mechanism that works with a telescope to track stars/planets etc. I am completing the repairs and would like to time it or evaluate how it is running. Any Help? Regards, Henry Gordon Uber [EMAIL PROTECTED] Reynen Uber Web Design http://www.ubr.com/reyubr/ Webmaster: Clocks and Time http://www.ubr.com/clocks/
Re: Request for postal address
From the USNO Web page: http://www.usno.navy.mil/ Superintendent U.S. Naval Observatory 3450 Massachusetts Avenue, NW Washington, DC 20392-5420 USA (202) 762-1437 [EMAIL PROTECTED] wrote: Hello, I am looking for the postal address of the US Naval Observatory at Washington DC Could someone help ? Thank you very much for you answer. Henri GOAS. Gordon Uber [EMAIL PROTECTED] 3790 El Camino Real, Suite 142, Palo Alto, CA 94306 Reynen Uber Web Design http://www.ubr.com/reyubr/ Webmaster: Clocks and Time http://www.ubr.com/clocks/
Re: Web site address.
Hebri, The USNO Time Service Department is at http://tycho.USNO.navy.mil/ This page cross links with the main USNO page at http://www.USNO.navy.mil/ For many links on Clocks and Time see my Web page at http://www.ubr.com/clocks/ . Gordon At 05:22 AM 10/7/98 , [EMAIL PROTECTED] wrote: Hello, I am looking for the web site address of USNO ( U.S. Naval Observatory ). Could someone help ? Thank you for your answer. Henri GOAS. Gordon Uber [EMAIL PROTECTED] 3790 El Camino Real, Suite 142, Palo Alto, CA 94306 Reynen Uber Web Design http://www.ubr.com/reyubr/ Webmaster: Clocks and Time http://www.ubr.com/clocks/
Re: Why 360 degrees?
The Babylonians developed their sexagesimal degree system in about 300 BC. (Their sexagesimal number system is much older.) It was used for astronomical tables at that time. The circle was first divided into sixths, and these were divided by sixty into degrees, thus, our 130 degrees would be (2 10), or 2 sixths plus 10 sixtieths of a sixth. The sixth is approximately equal to our present radian, which might have been why it was chosen; it is also easy to divide a circle into sixths by marking off radius-length chords. It is easier to determine _that_ something was done than _why_ it was done -- even today. As the saying goes, There are good reasons and then there are real reasons. For much more on Babylonian mathematics and astronomy see the writings of Otto Neugebauer. Gordon At 11:25 AM 7/8/98 -0700, Andrew B. Johnson wrote: Why did cartographers and others settle on a compass divided into 360 degrees? Why not simply 60, to match the further divisions into 60 minutes and 60 seconds? Or, if we want to recognise the four directions of the compass, why not into 240 degrees? Thanks for your help with this simple question. - andrew johnson berkeley california
Re: sundial help
Greg, Many math books and handbooks have tables of tangents; many pocket calculators will calculate them, and computer spreadsheet programs usually can calculate them also. The cotangent is the reciprocal of (that is, one divided by) the tangent. Also, the cotangent of an angle equals the tangent of 90 degrees minus the angle. See the example below. While it is possible to calculate a tangent from a formula, it is easier to get it by one of the methods above. The tangent of 0 degrees is 0; the tangent of 90 degrees is infinite, and the tangent of 45 degrees is 1.00. These are sometimes handy values to know. Some of these calculators or spreadsheets use angles in radians rather than degrees. Experimenting with the example below will show if they do. If necessary to convert an angle to radians: multiply by pi (3.14159) and then divide by 180. Also, some methods start with degrees and fractions, others use degrees, minutes and seconds. As an example, using your 11.9 degree value: the tangent of 11.9 is 0.2107 1 / 0.2107 = 4.7453 2 inches * 4.7453 = 9.4906 inches Alternately, 2 inches / 0.2107 = 9.4906 inches Or: 90 - 11.9 = 78.1 tangent of 78.1 degrees = 4.7453 Good luck with your sundial. Gordon At 09:18 AM 7/5/98 -0700, you wrote: I am building a sundial based on an example in Albert Waugh's book Sunidals Their Theory and Construction, p. 137. My problem is in computing lines of declination, however. I live in Washingotn DC at approx. 39d West Lat. 77d N Long. I'd like to trace the sun's path for one particular day, July 4, 1998. I believe the declination for that day is very close to +22d.54.34.9 and the sun's altitude in degrees for various times are as follows: 4:00-8.5 This will not cast a shadow. The sun is below the horizon. 5:00 1.6 Shadow is 71.6 inches long; impractical to use. 6:00 11.9 7:00 23.1 8:00 34.6 9:00 46.3 10:0057.6 11:0067.7 12:0073.7 13:0071.0 14:0062.1 15:0051.1 16:0039.5 17:0027.9 18:0016.5 19:005.7 20:00 -4.6 This will not cast a shadow. The book states that all I must do is take the cotangent of these altitude numbers and multiply by the height of my perpendicular style (which is 2 inches) then measure out to the appropriate hour line. My problem is that I cannot figure out what a cotangent is or how to calculate one. Please help and send a detailed formula with examples so I can compute the cotangent for other numbers. Thanks a lot in advance. -- Fiddler's Green We Design and Install Renewable Energy Systems Solar Energy...Live the Good Life! Greg Milsom, Owner PO Box 1200 Bowie, Maryland 20718 Phone/Fax: (301) 210-7669 http://www.radix.net/~green
Re: International Time Zones
In 1870 Charles F. Dowd of Saratoga, New York proposed the standard U.S. Time Zones for railroads. In 1872 these were adopted for U.S. and Canadian railroads. They had 1-hour intervals between zones. Sandford Fleming of Canada proposed these for worldwide use in 1876. These zones were gradually adopted, e.g., Canada in 1883, Liberia in 1972. The time zones are associated with and followed international adoption of the Greenwich Meridian and GMT. Cf. the First International Geographical Congress of 1871, the Seventh in 1883. The International Meridian Conference of 1884, Resolution V, established the universal day (GMT). At the end of that conference Great Britain proposed standard time to be used as local civil time, the intervals between zones to be multiples of ten minutes of time. This proposal was withdrawn. The conferences established GMT, and countries combined this with the Dowd/Fleming proposals to define their own standard times. For details see (e.g.) Greenwich Time and the Longitude by Derek Howse. This includes a table of adoption dates for each country. Gordon Tony wrote the foolowing: Fellow Shadow Watchers, Can anyone tell me when (or if) the system of=20 International Time Zones was formally established/recognized and by what=20 authority? Did it just evolve from each country's individual needs and=20 interpretations or was there an international conference at some stage? I have the British Admiralty World Time Zone Chart (5001) revised 1992=20 but the notes thereon give no indication of its origins. The information is requested for the notes to accompany a public dial and= =20 if anyone has this to hand it would save some urgent trawling through=20 reference material. Thanks in anticipation, Tony Moss
Unsubscribing from Sundials
Buddy, See http://www.ubr.com/clocks/sundial/sunlist.html Gordon Webmaster, Clocks and Time At 07:19 AM 6/10/98 -0700, Buddy L. Collier wrote: Would someone be kind enough to explain the procedure for 1. unsubscribing to this service and 2. subscribing to this service? I am changing servers and want to take this service with me. Thanks, Buddy
Re: Shortest day of the year
Glenn, Sunrise and sunset times are calculated by the US Naval Observatory page http://tycho.usno.navy.mil/srss.html for a location that you specify. I suggest searching the day of the winter solstice and days before and after to find minimum day length. Gordon You wrote: I would like assistance in finding out the month and day of the shortest day of the year. I appreciate all the help you can extend and contribute. Sincerely, Glenn A. Talaue -- | XII | Gordon T. Uber |XI| 3790 El Camino Real, Suite 142 | X \ /| Palo Alto, CA 94306-3314 | IX \ / | email: [EMAIL PROTECTED] CLOCKS and TIME: http://www.ubr.com/clocks/
Re: Shareware and freeware programs.
The Astroware 1 CD-ROM (copyright 1995) was sold by Network Cybernetics Corporation 4201 Wingren Road, Suite 202 Irving, TX 75062-2763 email: [EMAIL PROTECTED] WWW: http://www.ncc.com/ncc/ You wrote: I have learnt that a CD ROM containing astronomy shareware and freeware programs has been published. I don t know who is the editor but I know that it is call ASTROWARE 1. Does someone could indicated me wher I could buy this CD ROM. Best wishes for the new year. Henri GOAS. -- | XII | Gordon T. Uber |XI| 3790 El Camino Real, Suite 142 | X \ /| Palo Alto, CA 94306-3314 | IX \ / | email: [EMAIL PROTECTED] CLOCKS and TIME: http://www.ubr.com/clocks/
Re: Sundial for 6th grade
John, Just follow the details of the sundial experiment by Mark, another sixth grader. Instead of the pencil as described, stand a student up each hour (or two) as a gnomon and record the shadow position. His report of his experiment is in my CLOCKS and TIME pages under Education and then Sundial Experiment. Guaranteed to be correct for your latitude and longitude! Gordon You wrote: Date: Tue, 14 May 1996 17:49:15 -0400 From: [EMAIL PROTECTED] I am trying to find information about how I might construct a sundial using a person as the gnomon. I want to do this with my sixth grade students. (snip) Thanks, John Taylor -- | XII | Gordon T. Uber |XI| 3790 El Camino Real, Suite 142 | X \ /| Palo Alto, CA 94306-3314 | IX \ / | email: [EMAIL PROTECTED] Clocks Time: http://198.87.193.150/~clocks/clocks/clocks.html current: http://glen-ellyn.rice.iit.edu/~clocks/clocks/clocks.html
