John Carmichael wrote: > > Hello everybody! > > For a long time now I have wanted to make an "all business" scientific > horizontal string sundial which shows declination lines with a > longitude-corrected analemma offset from the meridian which shows 12:00 noon > in Standard Mean Time. The dial plate of a similar dial is shown opposite > pg. 200 in Mayall. > > Traditionally, a nodus is placed somewhere along the style. Since my style > is a cable, a little sphere attached to the cable would make a good nodus. > The objective would be to locate the nodus as far north from the dial center > as possible so that the distance between the winter and summer solstice > declination lines is maximized and the reading of dates and the analemma > would be more precise. But this distance can't be so far that the winter > solstice line overlaps the hour numerals. Even on my large 40" dial this > distance would be pretty small with limited precision. > > Now, what if instead of placing the nodus on the style, I use a tall > vertical pointed rod at the dial center for the nodus? (taller than the one > I am currently using) The space between the winter and summer declination > lines could then be much greater than the space projected from a nodus on > the style, the analemma would be larger and precision and legibility of the > declination lines and analemma would be much greater. Have any of you ever > seen a dial built like this? > > I know how to calculate and draw the declination lines for a vertical nodus > projecting onto a horizontal face. But nowhere can I find a formula for an > analemma projected onto a horizontal plane. In the new BSS June 1999 > Bulletin there is a good article by Allan Mills (pg.62) which deals with the > projection of analemmas on perpendicular, polar, south vertical, and even > curved surfaces. But no mention is given to the projection onto a > horizontal plane. Does anybody know what this formula is? Or better yet, > would any of you with computer sundial generators be willing to sell me a > computer generated drawing of the longitude corrected analemma and > declination lines for Tucson AZ (lat.:32 13' 18" N.; long.:110 55' 33" W.) > > Thanks for any of your thoughts and help with this problem. > > John Carmichael > http://www.azstarnet.com/~pappas
Hello John, Use ZWVLAK95.exe to calculate the EoT curves and declination lines for any flat plane. ( or use other computerprograms available ) I understand that you want to read the suntime with the shadowline of a style and the rest with the shadowpoint of a gnomon without any relation between the two. This is all right but the user has to know that he may not reverse the readings. I never saw such an arrangement. Happy dialling, Fer. -- Fer J. de Vries [EMAIL PROTECTED] http://www.iaehv.nl/users/ferdv/ lat. 51:30 N long. 5:30 E
