change e-mail
Dear Friends, please to note my new e-mail address from now: [EMAIL PROTECTED] Thanks Nicola Severino
Re: Azimuthal dial
Hello Bill, ( and others ) Thanks for your suggestion to use a cord to find the correct intersection point between a date line and the shadow line in an azimuthal dial. Although my program Spin is restricted to latitudes outside the tropics I calculated such a dial for latitude 0 degrees and for suntime. The picture is attached to this mail. It is clear that this dial can't be used during several weeks around the equinoxes. At the equinoxes the time can't be read at all. At that time, half a day the sun is due east and then jumps to due west for the rest of the day. Fer J. de Vries [EMAIL PROTECTED] http://www.iae.nl/users/ferdv/ Eindhoven, Netherlands lat. 51:30 N long. 5:30 E - Original Message - From: Wm. S. Maddux [EMAIL PROTECTED] To: [EMAIL PROTECTED] Cc: Mac Oglesby [EMAIL PROTECTED]; SUNDIAL SUNDIAL@rrz.uni-koeln.de; Fer J. de Vries [EMAIL PROTECTED] Sent: Friday, January 21, 2000 4:40 PM Subject: Re: Azimuthal dial snip. Fer, please forgive my tampering with your SPIN.GIF, in order to illustrate this suggestion. Bill Attachment converted: Macintosh HD:spin0.gif (TIFF/JVWR) (C6FC)
moondial eclipse results
Hi moondialists: Here are the results of my observations during the January 20 total lunar eclipse. We had excellent viewing conditions with low ambient light pollution. Readability: The gnomon's shadow disappeared when about 3/4 of the moon was darkened. Time accuracy: The sundial kept perfect time in the moments just before the gnomon's shadow disappeared and just after it reappeared. (I corrected for EOT and longitude). Declination/date readings: As some of us suspected, the date showed July 20th throughout the course of the evening. Color: the moon during totality was a yellowish ocher, and had a very three dimensional look. Just before the last sliver of white lunar surface disappeared, the moon looked very much like a picture of Mars with it's white polar cap! John Carmichael Tucson Az
Introductory astronomy sites
Hi all, Please can anyone point me at suitable URL's of basic astronomy, capable of answering questions of the why does the sun rise in the East and what causes the seasons? type. I have a contact at the local museum who is putting together an astonomy/sundial trail for primary schoolchildren and he needs background material. He will also be teaching the children to make cardboard dials, so we might get some more recruits at some time in the future! Thanks in anticipation, John -- Dr J R Davis Flowton, UK 52.08N, 1.043E email: [EMAIL PROTECTED]
Re: Kukulcan Equinox Phenomenon
Hello Roger, Welcome back--you've been missed. And thank you for the very interesting account of your investigations at Chichen Itza. Best wishes, Mac
Kukulcan Equinox Phenomenon
A highlight of my recent trip to Mexico was the Mayan ruins at Chichen Itza, in particular, El Castillo, the Temple of Kukulcan. This great pyramid is designed to mark the yearly cycle of the sun. Each of the four faces represents a season. Each of the four stairs has 91 steps, the number of days in each of the four seasons. The temple at the top represents the 365th day. The winter solstice sun just grazes the north face as the 45 degree angle equals the noon azimuth. (90-lat 20.666 - dec 23.44 - semidiameter .25 = 45.6 degrees. The light and shadow phenomenon of the equinox is world famous. See http:www.piramideinn.com/equinox.htm. The corners of the nine platforms cast a series of triangles on the stairway. As the sun sinks, the triangles of light move up creating the illusion of a serpent ascending from the ground to the temple. Tens of thousands come to this site at the spring and fall equinoxes to witness this remarkable phenomenon of the serpent descending to the ground as the sun rises and then ascending in the afternoon as the sun sets. The show takes over 3 hours and peaks near sunset when all nine triangles of light show the whole serpent. I could not find a good technical analysis of the phenomenon. The description in a booklet I bought has serious flaws. Most descriptions have more mysticism that facts. I asked myself if sundial design math could elucidate the phenomenon. Declination lines are the solution! The concept of declination lines is familiar to most of you. These lines are the path of the tip of the gnomon shadow for various dates and solar declinations. When the declination and latitude have the same sign, these lines are hyperbolic curves towards the gnomon. When the latitude and declination signs are contrary the lines curve away. On the equinox, the declination lines are straight lines. This is a universal phenomenon. The path of all shadows cast on any plane surface at any latitude are straight lines. On the horizontal plane, the equinox declination line is due east west. On a south facing vertical plane the line is horizontal. On a vertical declining plane, the declination line is sloped at an angle equal to the Substyle Distance (SD) of a vertical dial on that plane. The usual vertical declining design equation applies. Cot SD = Sin Lat / Tan Dec where Dec is the declination of the vertical plane from south. This special case of the straight declination line on the equinox is the basis of the Kukulcan ascending serpent effect. At Chichen Itza, the latitude is 20.666 and the orientation of the pyramid is 18 degrees off the north south axis. In this case, the formula reduces to SD = 39 degrees. This is exactly the angle the staircase of the tower makes with the horizontal plane. This explains the movement of the shadows along the face of the staircase creating the illusion of the serpent ascending as the sun sets. Each triangle of light and shadow is in effect a separate gnomon casting a shadow moving in a straight line at a 39 degree slope. A remarkable phenomenon, simply explained with the mathematics of sundials. This investigation required a lot of direct experimentation. I had to built several sand castle models on the beaches of Cancun and Isla Mujeres to test the solar orientations. I may now have to build one at home, adjusting for the latitude difference by tilting the model by 30 degrees. This should demonstrate the effect just as well as the original but snow may not be the appropriate construction material. Have any of you witnessed the event? Do you know of other examples of light and shadow shows built into solar oriented structures? Do you know of any good references to more complete technical analyses of the phenomenon at Chichen Itza? Roger Bailey Walking Shadow Designs N 51 W 115 Please note the new address. My ISP (banff.net) went bankrupt.
Re: Kukulcan Equinox Phenomenon
There is an error in the formula for Substyle Distance in the original posting. I transcribed from my rough notes incorrectly. The correct formula, from Waugh, is Tan SD = Sin Dec / Tan Lat. With the latitude of 20.666 and wall declination of 18 this solves to the angle I quoted, 39.32 degrees. The corrected URL is http://www.piramideinn.com/equinox.htm. Be patient as this server is often busy. There are some good pictures showing the equinox serpent at http://web.kyoto-inet.or.jp/org/orion/eng/hst/maya/chichen1.html The serpent is formed from shadows of the corners of the pyramid cast onto the vertical edge of the staircase. Roger Bailey 51 N 115 W At 07:56 AM 1/22/00 -0600, Warren Thom wrote: Hi Roger, The Mayan pyramid sounds interesting. Thanks for posting. I had a problem with the link in your message. I did find the following: http://www.mont-acad.pvt.k12.al.us/projects/civ/beau/temp.html I am still trying to picture how the snake image is produced. You did give a good account. Warren Thom
Re: Kukulcan Equinox Phenomenon
Hi Roger, The Mayan pyramid sounds interesting. Thanks for posting. I had a problem with the link in your message. I did find the following: http://www.mont-acad.pvt.k12.al.us/projects/civ/beau/temp.html I am still trying to picture how the snake image is produced. You did give a good account. Warren Thom Roger Bailey wrote: A highlight of my recent trip to Mexico was the Mayan ruins at Chichen Itza, in particular, El Castillo, the Temple of Kukulcan. This great pyramid is designed to mark the yearly cycle of the sun. Each of the four faces represents a season. Each of the four stairs has 91 steps, the number of days in each of the four seasons. The temple at the top represents the
Re: Kukulcan Equinox Phenomenon
Hi Roger, This is the link to the ruins with the two // http://www.piramideinn.com/equinox.htm Warren Thom, Roger Bailey wrote: The light and shadow phenomenon of the equinox is world famous. See http:www.piramideinn.com/equinox.htm. The corners of the nine platforms
