Hi Chris, I have not given up on a polar orientation surface yet, but I don't think it will work because it needs a line to cast a shadow and I have not been able to picture the correct effect of a line shadow on a polar plane. A "planispheric projection" might give the location of where the sun is setting. I will work on it.
I do feel for sure that a horizontal line - directed to where we want to know if the sun is shining - can tell us something - but other places on the map are not correct - only to where the line is directed. Thanks - Warren Chris Lusby-Taylor wrote: > In reply to Warren Thom's query: > > >on a dial map WHERE the sun is setting by a shadow. I like the opening > >screen of > >the NASS home page that shows the area of daylight on the planet -- but > >that is > >the computer screen -- I like "real" maps. Has this been done on a dial? > >Fred > >Sawyer showed in the Compendium the method Foster used to map TIME around the > >world. Any ideas on this from anyone? > > > > John Carmichael asks: > >would this work? A polar dial with a world map on the face with moveable > >gnomon mounted to a set of hourlines(maybe etched on clear glass) that can > >be shifted according to the date? > > >This is rather hard to expain, but we can discuss it in Hartford. > > No, I don't think it would work, except at the equinoxes, as the edge of the > polar dial's shadow would not take declination into account, so would show > sunrise at 6 o'clock regardless of season. > > An elegant and obviously correct solution is a standard terrestrial globe. > It must, of course, be set up with its location on top and in the correct > orientation. > > Off hand, I cannot think of any solution with a plane map. If one exists, I > imagine > the map might use the planispheric projection of the astrolabe. > > Chris Lusby Taylor > Newbury > Berks. > England.
