I have been thinking about a dial described by Ing. Gianni Ferrari in the March issue of the NASS Compendium. The article is based on Ptolemaic coordinates. A background was laid by Fred Sawyer in the September 1998 issue. Starting simple with the dial on page 19 and labeled figure 12. Questions:
(a) Can (should) the time line be extended upward to the south to give hours after 6pm during the summer? (I think so.) (b) With corrections for the equation of time and longitude difference from the standard time zone meridian on the declination scale, by moving the E-W rod up or down (like an analemma or figure 8 fashion) -- can the time show clock time fairly accurately? (c) How might I start, if I wished to look at Italian hours (hours to sunset) on any of the dials described in the article on Ptolemaic coordinates? I know Italian hours can be considered as great circles on the globe. I find the Compendium fascinating. I am stumped by the quiz "Emerson's Quandary" this time -- but I will work on it . Fer deVries program for the Pingre dial is amazing and the article on Chapuchin dial is well done. Thanks to all -- Warren Thom (Lat=41.649 Long=88.096)
