Hello Luke, I think I understand what Fer means about using sundials as the original users did in their time. I agree with Fer in feeling that a sundial should be what it is - an indicator of sun time, the time of here and now. Local Apparent Time is pure time. All other forms and methods, i.e., mean time, standard time, time zones, the EOT etc., are man made "perversions" of true sun time. I do admit, however, that in our modern age, a sundial is not suitable for our current time keeping requirements. The world has become too fast and crazy. In a way, I wish we could return to the slower paced times in which LAT was satisfactory for every man's needs. A Chinese shadow sharpener would not be a perversion as it only allows for more precise reading of LAT. Well, perhaps it would be a semi-perversion, since the original users probably could have cared less for that kind of precision.
May you have much sunshine! Charles At 09:10 AM 5/3/99 -0800, you wrote: >Hello Fer, > > Yes I understand, and with my SunClock I indeed use the center of the >projected solar disk to bisect the Analemma(and IMHO, with great >precision and accuracy) BUT it is my understanding that craftsmen of the >past made use of the fact that the contrast of a cast shadow can be best >resolved if one "offsets" the hour lines one would normally draw by the >semi diameter of the sun i.e., line up the hour line with the limb not >the center. This was meant, I assume, to improve its precision/accuracy. >Charles, in his e-mail, brings up Chinese shadow sharpening techniques, >this is exactly the direction I was hoping this thread would take, not >about "enforcing" paradigms. > > >Best Regards, > >Luke > > > >fer j. de vries wrote: >> >> Luke Coletti wrote: >> > >> > Hello Roger, >> > >> > Any thoughts on how one should calculate solar coordinates to be most >> > precise/accurate? Most solar coordinates are computed for the center of >> > the solar disk, I would like to hear feedback (since I don't believe >> > this topic has come up yet) on using coordinates based of the solar limb >> > (instead of the center) to increase both precession and accuracy of the >> > cast shadow. I await another stimulating thread. >> > >> > Best Regards, >> > >> > Luke >> > >> >> Luke, >> >> If you use a rod as shadow caster or a hole in a disk to produce a spot >> of light to read a sundial you have to calculate the coordinates of the >> center of the sun. We than read the time at the center of the shadowline >> or at the center of the light spot. >> >> If you use an edge of a solid body then perhaps you may use the >> coordinates of the limb of the sun. >> >> But please, have in mind we are dealing with sundials, not with >> instruments to read a time in parts of a second or minute. >> >> Don't forget the history of sundials. How did people the things at their >> time? >> In our time we have other instruments to measure time as precisely and >> accurate as we want. >> A sundial still has to reflect to the older times and a suntime hour is >> irregular in length. >> Even then I can construct precise and accurate dials. >> >> Happy dialling, Fer. >> >> -- >> Fer J. de Vries >> [EMAIL PROTECTED] >> http://www.iaehv.nl/users/ferdv/ >> lat. 51:30 N long. 5:30 E > >
