I am looking for info. on how to build an analemmatic sundial ( we call them "cadran analemmatique" in french). There are a few of these in Europe, (near the church of Brou in Bourg-en-Bresse, France) is one of them.
The dial is horizontal and the gnomon is vertical and moved along the North-South axis during the year. This movement is my problem: I read in a book that d( movement of the gnomon) is equal to tg (Decl. of sun)/cos (lat.) For example, on June 21st in lat. 45N , the gnomom should be moved tg 23.45/cos 45 , ie. approx. .42/.7 or .6 times diam./2 along then N-S axis to give the time correctly. It doesn't seem to work right according to my calculations. Please help!
