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.
