Thanks to Chris, for the clever graphical explanation showing especially the
discontinuities which support his recommendation to look at John Shepherd's
work on the beautifully designed and executed Richard D. Swensen Sundial at the
University of Wisconsin - River Falls.
http://www.uwrf.edu/sundial/
Not only is the sundial elegant, the web pages are too!
The continuity of the analemma seems to respect Earth's rotation and revolution
with much more fidelity than tables which give the "accuracy" of the dial by
cataloguing the EoT with the (usually) Gregorian Calendar. That is to say the
"in situ" analemmae prevent the inaccuracies introduced by the "calendar
problem" that Chris illustrates so clearly.
The only place where the "calendar problem" rears its ugly head on Shepherd's
dial is on the week indicators on the analemmae themselves. Too bad, eh?
(That's the Canuck coming out, eh! ) The Standard Time vs Daylight Time
problem is neatly avoided.
Precision:
The close-up photographs clearly show the precision of this Sundial (or
heliochronometer [sun-time-measurer], I guess), indicating an optimized
diameter for the gnomon.
Perhaps Professor Shepherd would care to share his thinking on the topic of
precision with us.
Analemmae:
It appears that the calculations were done in general; then the location, scale
and orientation variables were set in; resulting in some sort of output that
was used as input into a CAD program; which in turn gave those beautiful
analemmae which were then "pasted" onto the wall using another scaling factor.
Perhaps Professor Shepherd would describe how he went from those terrible
recursive functions which produce the EoT to getting a template for those
analemmae.
Thank you.
--
Tom Semadeni O
[EMAIL PROTECTED] o
aka I (Ned) Ames .
Britthome Bounty ><<((((*>
Box 176 Britt ON P0G 1A0
'Phone 705 383 0195 fax 2920
45.768* North 80.600* West
