Thanks for the graph, Luke. If I take +/- 20 sec as the accuracy of a
very good sundial, then I see that I have to start correcting for
refraction around 10 deg altitude, i.e., the first hour after sunrise
and the last hour before sunset. Since Pete Swanstrom's earliest
observation is at 7:10
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.
Yes, I tried it with POVRAY. I defined a stone and a long
On Wed, 17 Jun 1998, Doyle J. Groves wrote:
Sounds interesting. Could you perhaps make this movie available to the
group or at least email me a copy?
I've made the files available at
http://www.ph-cip.uni-koeln.de/~roth/movie.html
As I mentioned they are not what can be done.
You'll need
Arthur Carlson wrote:
Near sunrise and sunset, atmospheric refraction displaces the image of
the sun by about half a degree, which should show up as an error of
nearly 1-1/2 min, dial fast at sunrise and slow at sunset. I would be
interested in hearing if you can measure this effect. I
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
