Thank you John! I too have an excellent reference to a proof that circles project to circles.
I found this graphical/mathematical article to be easily understood. In addition to the proof, the author goes on to tell how to make such a projection. I'm currently adapting his equations to a VB6 program to draw a projection for any latitude. Go to http://gbms01.uwgb.edu/~dutchs/structge/stereo1.htm Enjoy Charlles > -----Original Message----- > From: [EMAIL PROTECTED] > [mailto:[EMAIL PROTECTED] Behalf Of John Schilke > Sent: Friday, April 28, 2000 1:14 AM > To: Sundial Mail List > Subject: Stereographic projection > > > Greetings! > > It is only in the last day or so that I have noted the discussion > concerning > the stereopgraphic projection, that wonderful invention of the ancients to > solve problems involving the astronomical triangle. It took a bit of time > to find the reference in a old book from my college days, but I'd like to > add a rather pretty discussion of the proof in > David Hilbert and S. Cohn-Vossen, _Geometry and the Imagination_, > New York, 1956, Chelsea Publishing Co., a translation by P. Nemenyi of the > famous _Anschauliche Geometrie by these authors; pp. 248-59. > I just thought someone might like to check it out, too. > > John > >
