RE: Chilean Quake May Have Shortened Earth Days

The position of the pole isn't constant anyway. Here is the Wikipedia article on the Chandler wobble. http://en.wikipedia.org/wiki/Chandler_wobble And here is a photo of the Chandler tombstone in Cambridge MA. http://www.dickkoolish.com/rmk_page/RMK_Pictures/Astronomers640/SChandler.JPG I also

Re: DST Misconceptions

Even if the myths are busted, some people still like it. Most of our lives are not symmetrical around noon, but are biased to the afternoon and evenings, so having more daylight then is a better match for our daily activities. In Boston, the summer solstice sunrise is at 5:08 AM. That's two

Re: DST Misconceptions

The problem with all these arguments is that they assume that all hours of the day are equally useful, and they obviously are not. A sarcastic or funny joke doesn't change the fact that most people today have more waking hours after noon than before noon. Hi 2010/3/16 Chuck Nafziger

Re: Russell Porter Sundial?

Here is one of the Porter sundials in Springfield VT. http://www.dickkoolish.com/rmk_page/RMK_Pictures/S60-07-31-06/IMGP0754.JPG Friends, Is there a conventional name (like horizontal', equatorial', polar' and so on) for the sundial constructed as shown below? Am I right thinking that

Re: Polar sundials

Try this experiment: Draw a circle that represents the earth and draw a vertical line through it for the polar axis. At 45 N latitude, draw the profile of a vertical dial. At 45 S, draw the profile of a horizontal dial. You will see that they are in the exact same orientation with respect to

Possible sundial in TV commercial

I've seen a United Parcel Service (UPS) TV commercial that includes something which looks like a possible sundial in the background. Here is a shot off the TV screen. Sorry for the poor picture quality. http://www.dickkoolish.com/rmk_page/RMK_Pictures/Sundial_TV/DSC_0167.jpg

Re: Special Seasonal Dates

The date of earliest sunset depends on Latitude and is not always Dec 14. See: http://www.idialstars.com/eass.htm Dear Colleagues In the depths of a freezing Northern winter, there's time to think about days of special interest. There are six significant solar dates around this time of

Re: Earth movements

The short answer is that any coordinate specification has to be given in reference to a particular datum. Here's the Wikipedia article on datums: http://en.wikipedia.org/wiki/Datum_%28geodesy%29 Bravo, Tony Finch, for sharing this. I had no idea location was so complex! Thank you. Mac

Re: solar tracking sundial

The equitorial drive of a telescope mount also turns at the rate of the earths rotation but in the opposite direction, so as to keep a specific point in the sky in the telescopes field of view. But you have different rates for different kinds of objects and you have to account for refraction.

Re: Fwd: Prague Clock

For eclipses to happen, the 'line of nodes' must be aligned with the sun. This happens roughly every six months and create the 'eclipse seasons' during which eclipses are possible. htmlHEADLINK rel=stylesheet type=text/css href=/netmail/static/deg/css/wysiwyg-3933289048.css media=all META

Re: varying speed?

People might be interested in the book The Sun in the Church by Heilbron. It's about using meridian lines in cathedrals for solar measurements. http://www.math.nus.edu.sg/aslaksen/teaching/heilbron.html Brent If you measure the transit of a star (or any celestial body) through the meridian

Re: Russell Porter Garden Telescopes

I know some folks in the Antique Telescope Society who have real, original Porter garden telescopes. Here's a photo of two of them together: http://www.dickkoolish.com/rmk_page/RMK_Pictures/D80-11-14-10/DSC_0147.jpg Hello All, Some of you may be interested in this if you have some spare

Re: Longitude grid vector file

The problem is that the shape of the grid, as well as all the geographic features depends on the map projection. See: http://geology.isu.edu/geostac/Field_Exercise/topomaps/distortion.htm To first order, you take a geographic object as a list of lines between lat-lon points, use the map

Re: Lunar Eclipse of 2011 Dec 10

More information is here: http://eclipse.gsfc.nasa.gov/OH/OH2011.html I thought some of you might be interested in the upcoming lunar eclipse on the 10th of this month. I've attached a diagram showing the regions of visibility of the eclipse. Brad

Cartoon about B.C.

Here's a New Yorker magazine cartoon about B.C. http://www.condenaststore.com/-sp/There-I-go-still-writing-B-C-on-my-checks-New-Yorker-Cartoon-Prints_i8546253_.htm --- https://lists.uni-koeln.de/mailman/listinfo/sundial

Re: Transit of Venus

Here's an article from the Sky Telescope website about the transit. http://www.skyandtelescope.com/observing/home/Transits-of-Venus-Explained-152556885.html Dear All, As several have noted, there is a Transit of Venus on Tuesday/Wednesday next week. For those in the U.K. the 2012

3D pictures of the Venus transit

This web page has some 3D pictures of the Venus transit as well as some time-lapse sequences. http://sweiller.free.fr/Venus/Venus-Transit.htm --- https://lists.uni-koeln.de/mailman/listinfo/sundial

Re: Eclipse shades

The commonly stated resolution of the eye is about a minute of arc. The angular size of Venus during the transit was just under a minute of arc, so it would have been a difficult observation under any circumstances. A minute of arc is about 1 inch at 100 yards, i.e. an American 25 cent piece at

RE: Elegant Gnomon

Here are some pictures of the Paul Manship dial at the Phillips Academy in Andover, Massachusetts, USA. http://www.dickkoolish.com/rmk_page/sundials/phillips_andover.html EXCELLENT! From: sundial [mailto:sundial-boun...@uni-koeln.de] On Behalf Of Tony Moss Sent: Monday, August 27, 2012

Re: From the New York times

Last November, Sara, Ken, Roger Sinnott and I visited Wellesley College to check out the observatory and a couple of sundials on the campus. The pictures are here: http://www.dickkoolish.com/rmk_page/pictures_112312.html Sara

Re: A prize for the worst 'non-dial', of the year?

Search Google Images for wrist sundial and you will see this item and a bunch of others. And there's always the Pocket Stonehenge: http://www.ohgizmo.com/2006/06/19/stonehenge-pocket-watch/ Hi David, That is a Fossil wrist sundial. The Fossil company, well known for their watches, purses

Re: Art in dialling

There's another Paul Manship dial in Andover, Massachusetts, USA. http://www.dickkoolish.com/rmk_page/sundials/phillips_andover.html Hi Mario, Have a look at http://www.1939nyworldsfair.com/worlds_fair/wf_tour/statues/fates_of_man.htm for the amazing dial by Paul

Re: Art in dialling

There's another Paul Manship dial in Andover, Massachusetts, USA. http://www.dickkoolish.com/rmk_page/sundials/phillips_andover.html Hi Mario, Have a look at http://www.1939nyworldsfair.com/worlds_fair/wf_tour/statues/fates_of_man.htm for the amazing dial by Paul

Re: Is East/West always at exact 'right-angles', to North/South?

While longitude lines are great circles, latitude lines are small circles. David Patte wrote: Yes, at the point of intersection they are, but don't forget though that lat and long are great circles, not straight lines. Of course, there is no east or west at the poles.

Re: Is East/West always at exact 'right-angles', to North/South?

This would be the starting azimuth of the great circle route from your location to Mecca. Here's a web page that does this: http://www.qiblalocator.com/ Douglas Vogt wrote: Reminds me of someone  a year or so ago who developed a method of determining the east of Mecca for prayer purposes

Re: Is East/West always at exact 'right-angles', to North/South?

The oblateness of the earth is about 1/298. The Wikipedia page on the figure of the earth is here: http://en.wikipedia.org/wiki/Figure_of_the_Earth Here's another page on the shape of the earth: http://en.wikipedia.org/wiki/Earth_radius The WGS-84 ellipsoid gives the equitorial radius as 6378 km

Large dial in New Milford CT

A friend sent me a link to some information about a large equitorial dial at the McCarthy Observatory in New Milford, Connecticut. It does not seem to be in the registry. http://www.mccarthyobservatory.org/?page_id=163 http://www.mccarthyobservatory.org/?page_id=1197

Humorous video about dates and times

Making sundials is easy compared to the problem of writing software to keep track of dates and times. http://www.wimp.com/problemtimezones/ --- https://lists.uni-koeln.de/mailman/listinfo/sundial

Re: sundials in schools

There are astronomy programs like Stellarium and smartphone apps that give the azimuth of the sun at a given time. That and a protractor will give you true north. I would also love to see sundials in schools. Not just an analemmatic dials but the multi dial as well. This is why I am trying

Re: Map required

A simple rectangular projection where Longitude is the X coordinate and Latitude is the Y coordinate also has straight and perpendicular lines. And it can go all the way to 90 North. Of course, longitude is very distorted at the poles. http://en.wikipedia.org/wiki/Equirectangular_projection

RE: Veteran's Memorial Aperture Dial - Anthem Arizona

The declination of the sun around January 30th is the same as on November 11th. So any alignments on November 11th should also occur in late January. For example, these are also the dates of MIT Henge, where the setting sun shines down the 800 foot long Infinite Corridor at MIT in Cambridge MA.

Solstice alignments at the Taj Mahal

I saw the article today about some solstice alignments at the Taj Mahal. http://www.livescience.com/49660-taj-mahal-gardens-align-solstice-sun.html?google_editors_picks=true --- https://lists.uni-koeln.de/mailman/listinfo/sundial

Re: Please help identify this architectural sundial and location.

https://www.flickr.com/photos/suzanne-gibson/8377866276 Please help identify this architectural sundial and location recently posted on Flickr. https://www.flickr.com/photos/schraeglage-urbex/19116095082/in/explore-2015-06-24/ Larry Bohlayer

Re: due east

> Mark Gingrich wrote: > Indeed. And here's a curious bit of related trivia: If you > start due east from *any* latitude and travel a great circle > route -- i.e. "straight" -- a distance of one quarter of the > Earth's circumference, you *always* end up on the equator. > > This also works from

Re: due east photos

At any point on the earth, there is one great circle that is tangent to your latitude circle. That means that at that infinitesimally small point, both circles point in the same direction, i.e due east, but only at that point. Also note that the plane that cuts the earth at any latitude is

Re: Possible sundial in movie

Here's an example of a dial with an equitorial band all around. http://www.dickkoolish.com/rmk_page/sundials/phillips_andover.html > On Mon, Sep 28, 2015 at 3:24 PM, Dan-George Uza > wrote: > >> Hello, >> >> Tonight I saw the trailer for "The 100-Year-Old Man Who

Re: Possible sundial in movie

"Turtles all the way down" of course. :-) https://en.wikipedia.org/wiki/Turtles_all_the_way_down > Beautiful dial and setting, Dick! > But please explain for us: > What's supporting all those turtles?!? > > Dave > > Sent from my iPhone > >> On Oct 1, 2015, at 3:53 AM, kool...@dickkoolish.com

Neat video showing how sunrise moves

A student video showing how sunrise moves along the horizon. https://www.youtube.com/watch?v=UzOkTjxhR3Q --- https://lists.uni-koeln.de/mailman/listinfo/sundial

Moon phase calculator

There was a recent discussion about moon phase calculation. Check out the slide rule and circular calculators at http://www.moonstick.com/ --- https://lists.uni-koeln.de/mailman/listinfo/sundial

NY Public Library photos online

The New York Public Library has put 187,000 pictures online. I don't know if there is a top level text search, but if you pull up an, image, there is a text search box at the top of the page. So you can type in "sundial" and see what images in the collection match.

Re: NY Public Library photos online (forgot the link)

Sorry, I forgot to include the link. http://publicdomain.nypl.org/pd-visualization/ > The New York Public Library has put 187,000 > pictures online. I don't know if there is a > top level text search, but if you pull up an, > image, there is a text search box at the top > of the page. So you

Re: A Happy Leap Year Day to everyone

There's a Wikipedia article about leap years. https://en.wikipedia.org/wiki/Leap_year > > Frank, > > Why have you sent your wishes for a Happy Leap Year Day on February 24 ? > > Willy Leenders > Hasselt in Flanders (Belgium) ---

Re: Happy Nowruz!

In Boston MA USA, today was Evacuation Day, which celebrates the evacuation of British troops from Boston during the Revolutionary War. :-) https://en.wikipedia.org/wiki/Evacuation_Day_%28Massachusetts%29 ---

Re: Unusual bi-annual sundial

Something else that happens twice a year is MIT Henge. http://www.dickkoolish.com/rmk_page/mithenge.html - Original Message - From: "Art Krenzel" To: "sundial@uni-koeln.de" Cc: Sent: Wed, 18 Jan 2017 22:41:15 + Subject: Unusual

Re: Dial face colouration

18% gray is used because that was thought to be the average reflectance of photographic subjects. - Original Message - From: "Patrick Vyvyan" To: "John Lynes" Cc: "sundial list" Sent: Sun, 26 Feb 2017 13:01:10 -0300

Re: Astronomy Picture of the Day (Again)

Of course the first analemma picture was taken by Dennis DiCicco. http://twanight.org/newTWAN/photos.asp?ID=3001422 - Original Message - From: "Robert Terwilliger" To: Cc: Sent: Wed, 21 Dec 2016 08:43:28 -0500 Subject: Astronomy Picture of

Solstice sundial

This dial tells you that it is the solstice. https://apod.nasa.gov/apod/ap170621.html --- https://lists.uni-koeln.de/mailman/listinfo/sundial

Analemma crossing dates

A friend asks if the dates where the north and south going branches of the analemma cross have a special name. Around mid-April and the end of August. --- https://lists.uni-koeln.de/mailman/listinfo/sundial

Article about Armenian sundials

This was sent to me by a friend. https://www.panorama.am/en/news/2019/02/23/Armenian-sundials/2076856 --- https://lists.uni-koeln.de/mailman/listinfo/sundial

Re: Can a sundial disprove Flat Earth?

Didn't Eratosthenes show that the earth was round by measuring the diameter? - Original Message - From: "Dan-George Uza" To:"Sundial List" Cc: Sent:Mon, 17 Jun 2019 16:04:58 +0300 Subject:Can a sundial disprove Flat Earth? Hello, In my country there is this growing Flat Earth

Zero magnetic declination at Greenwich

This might be of interest to dialists. https://www.theguardian.com/science/2019/aug/30/compasses-to-point-true-north-for-first-time-in-360-years --- https://lists.uni-koeln.de/mailman/listinfo/sundial

Re: Moondial question

You might look here and see if anything helps. http://www.moonstick.com/ --- On 2020-02-04 09:48, David Benton wrote: So I’ve been trying to find detailed information on Moondials and how to make them. Unfortunately, I’ve not found much out there on the subject. Does anyone here in our

Re: Aperture nodus geometry

Stenopiac image just means pinhole image. While pinhole images can look fairly sharp, they can't match the sharpness of a lens. The optimal pinhole for an 8x10 inch camera can resolve about 5 lines per millimeter, which will look sharp as a contact print. A good lens can resolve 100 lines per

Mobius Strip sundial at Brown University

https://www.brown.edu/news/2019-05-08/sundial -- --- https://lists.uni-koeln.de/mailman/listinfo/sundial

Re: Adjusting dial to new location

Steve tells me that the lack of longitude correction instructions was due to my choice of 'local solar time' as the time indication. When I use 'UTC-5' I get the instructions. --- On 2023-04-02 21:30, kool...@dickkoolish.com wrote: I tried the app. I used 40, -75 and 45, -70. It just said to

Re: Adjusting dial to new location

Depending on your choice of rotation axes, only two rotations are needed, one for the elevation of the pole and one around the gnomon for longitude correction. These are the two that correspond to the actual changes needed. If you are using the three orthogonal x, y, and z axes, then three

Re: Adjusting dial to new location

Assuming that a dial should read only local solar time is a rather limited view. While it might be of interest to the dial purist, it is not particularly useful to the general population and often requires a lot of explanation. And it makes us seem like an eccentric clique. The dial produces a

Re: Adjusting dial to new location

Rotating the dial plate around a vertical axis is wrong because the hours lines are not at constant angles. Rotating the whole dial around the polar axis is the correct way to adjust a local solar time dial to a different longitude, the time zone center, for example. Having a dial show the

Re: Adjusting dial to new location

I tried the app. I used 40, -75 and 45, -70. It just said to use a 5 degree wedge and said nothing about a longitude correction. I communicated to Steve privately last week. I said that a longitude correction was a rotation around the gnomon. Does anybody else believe this? One of the books, I

Sundicator

Somebody was interested in the Sundicator. I've got one.

Sundial article in Weatherwise magazine

There's an 8 page article about sundials in the July/August issue of Weatherwise magazine.

Re: Sundials at Train Stations

The eye/brain is very good at seeing lines, and can see lines thinner than the usual 1 arcminute given as the resolution of the eye. 20/20 vision is based on reading letters that are 5 arcminutes high that have 1 arcminute features (line width and gaps). So this might give you an idea of how big

Analemma exposure

The normal procedure when photographing the sun is to use a neutral density filter of density 5.0, which reduces the light by a factor of 100,000. So even of you took a picture a week through this filter, it's nowhere near the exposure needed to register the foreground image.

moonphase calculator

People on this list may be interested in the Moonstick slide rule moon phase calculator. www.moonstick.com

pinhole picture of a sundial

Thomas Harvey posted a picture to the pinhole photography mailing list of a sundial in Portland Oregon. http://web.pdx.edu/~harveyt/USsundialPin.jpg

Re: Rainbow geometry

There's a web page on rainbows and halos at: http://ds.dial.pipex.com/lc/atoptics/phenom.htm

Re: Commercial Offerings

The photo-3d list people maintain a different list sell-3d for commercial postings.

Re: Polar Alignmen

Amateur astronomers also deal with polar alignment when they have to set up an equitorial mount. This is usually done with a low power finder scope (6 to 8 power). If you can attach a finder scope to the sundial, this would be much better than trying to align by eye. Some finder scopes just

Aquitaine sundial

I've been given an Aquitaine ring sundial. I'd like to know how to compute one, but have been unable to find information in my sundial book collection or on any sundial web sites. -

Pinhole diameter

For pinhole imaging, the optimal diameter of a pinhole is one where the pinhole is the same size as the diffraction disk it produces. There is a calculator at: http://www.mrpinhole.com/calcpinh.php and a lot of information at: http://www.pinholeresource.com/pinhole.html -

Size of degree of latitude

http://pollux.nss.nima.mil/calc/degree.html this page will compute the size of a degree of latitude and longitude -

World’s first radio sundial dedicated in memory of Ron Bracewell

Sundial at the Very Large Array made from parts of an old radio telescope. http://news.stanford.edu/thedish/2013/10/02/worlds-first-radio-sundial-dedicated-in-memory-of-ron-bracewell/ --- https://lists.uni-koeln.de/mailman/listinfo/sundial

cartoon in the New Yorker

There is a sundial cartoon in the March 9th issue of the New Yorker magazine. I scanned it in and put it on my web page. http://linux.bbn.com/~koolish

Chaucers treatise on the astrolabe

http://www.fordham.edu/halsall/source/chaucer-astro.html

graph of refraction error

There is a graph of the refraction error at: http://www.cadastral.com/papersl1.htm

anybody use raytracing

There are free raytracing packages available that allow you to describe a 3-dimensional object and render an image of it with light sources placed at will. Has anybody used these to simulate sundials? Seems like it should work.

1998 sun/polaris dec table

The following web page has a table for every day of 1998, giving the declination of the sun, the equation of time, and the declination of Polaris. http://www.cadastral.com/eph1998b.htm

movie player for UNIX systems

Daniel Roth's movies can be played on UNIX systems with the XAnim program. It's available from: http://xanim.va.pubnix.com/home.html

lunar libration animation

I know this is slightly off-topic, but I thought it might be interesting. This is an animation of the lunar phases that clearly shows the libration. http://www.geocities.com/CapeCanaveral/5409/lunation.gif

Explanatory Supplement

After being out of print for many years, the Explanatory Supplement was re-written and re-published in 1992. It is now the Explanatory Supplement to the Astronomical Almanac, edited by Kenneth Seidelmann and is published by University Science Books, 20 Edgehill Rd, Mill Valley, CA 94941.

MIT Henge

We are coming up to the day when sunset lines up with the Infinite Corridor at MIT (Massachusetts Institute of Technology) in Cambridge, MA, USA. I may try and observe it this year. http://w3.mit.edu/afs/athena.mit.edu/org/p/planning/www/mithenge

Sundicator picture

I scanned the Sundicator and put an image on my web page: http://linux.bbn.com/~koolish Click on the small image to get the big image (296K).

glsaa sphere

A web search turned up glass spheres at: http://www.angelsandearthlythings.com/s-sphere.html

Re: a peculiar sharpener

Patrick Powers wrote: It is simply the pin hole camera effect again. Light passing through any small aperture is focused . As the hole's size is changed the focusing parameters are changed too. So with a fixed distance from hole to plate there will be one size that works. A different size

picture of sun tracking device

I've put a picture of what I think is a sun tracking device on my web page at linux.bbn.com/~koolish. If anybody has seen one or knows how it was used, let me know. There are no markings on it.

more on the bead in the hole

A paper recently put on the web about pinhole photography has a section about something called a 'Pinspeck Camera' that might have the same properties as the bead in the hole shadow sharpener. See: http://www.pinhole.com/resources/articles/Young/index.html and look down near the end of the

solar filter sources

A page of solar filter sources is: http://umbra.gsfc.nasa.gov/eclipse/970309/text/filter-sources.html

books on atmospheric phonomena

There's a page of books on atmospheric phonomena at: http://www.treasure-troves.com/astro/AtmosphericPhenomena.html One book that I like is: Greenler, R., Rainbows, Halos, and Glories, Cambridge University Press, 1980.

does this work

Take a look at this sundial: http://www.angelsandearthlythings.com/hp4500.html I think it has problems. Am I correct?

Re: The analemma

There is an article in the most recent edition of Sky and Telescope magazine about photographing the analemma. It describes how photos have been taken which show the movement of the sun. They rely on time lapse (either 365 or 12 exposures over the course of a year), with each exposure

NASA eclipse info page

There's a great web site for eclipse info, both solar and lunar at: http://sunearth.gsfc.nasa.gov/eclipse/eclipse.html

lunar perigee vs phase

The synodic month (full moon to full moon) averages 29.53 days, while the anomalistic month (perigee to perigee) is 27.55 days, so the phases drift with respect to perigee. see: http://www.treasure-troves.com/astro/AnomalisticMonth.html

bad sundial illustration

The cover of the June 2000 issue of Embedded Systems programming has a sundial with the gnomon pointing in the wrong direction. I've already emailed them about it. It's on my web page at: http://linux.bbn.com/~koolish with the full scan in: http://linux.bbn.com/~koolish

Re: The Swensen Dial WebCam is going again.

Isn't Beltane the other side of Candlemas? I am looking forward to an authoritative answer based on solar declination. Roger Bailey Beltane explanation (and other cross-quarter days): http://www.isleofavalon.co.uk/edu/g-bank/articles/beltane.html

suns angular diameter

From the web page: http://sunearth.gsfc.nasa.gov/eclipse/SEhelp/SEgeometry.html Eclipse geometry is complicated by the fact that Earth's orbit around the Sun is elliptical. As a result, the Sun's apparent semi-diameter varies from 944 arc-seconds at aphelion to 976 arc-seconds at perihelion.

Re: no mail ? Is it normal ?

Actually it is dark, but the lights are on. See the amazing photo at http://antwrp.gsfc.nasa.gov/apod/image/0011/earthlights_dmsp_big.jpg Daniel Wenger We amateur astronomers call that 'Light Pollution'. http://www.darksky.org/ida/index.html

Scientific Instruments Auction

Don Yeier, ex Vernonscope owner is having a scientific instruments auction on Saturday, May 19, 2001, in Candor, New York (near Binghamton). In addition to antique telescopes, binoculars, clocks, etc. the flyer says there is an Augsberg equitorial dial and other sundials. Catalog is $20.00

pinhole photo of Portland sundial

There's a pinhole camera photo of the Portland Oregon Union Station sundial at: http://web.pdx.edu/%7Eharveyt/C1.html

safe solar filters

See: http://www.mreclipse.com/Totality/TotalityCh11.html This is from Fred Espenak at NASA. http://www.mreclipse.com/Totality/TotalityCh11.html -

Re: Moon rise/set on the equinox

On March 20, the declination of the sun is 0, so it rises due east and sets due west. The moons declination on that day is almost -26 degrees so it rises south of east. The full moon rise this past Tuesday was almost due east. Unlike the sun, whose declination changes just a bit every day, the

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