I have given this question quite a bit of thought over the past 3 years, because the focusing sundial I sell is readable to a few seconds. It will not live up to its accuracy unless set properly. If a dial is well made, and matched to its latitude, then it only has to be levelled and properly aligned north. I have chosen solar noon as the best time for this, for several reasons, but the best reason is that the gnomon casts its shadow symmetrically at soalr noon, and you don't have to worry that you are reading the wrong part of the shadow's edge. Folks who have experimented with shadow sharpeners will know how hard it is to judge the mid-point of a shadow's penumbra. If the dial is not matched to the latitude, i.e.most store bought dials, then solar noon is the only time it can be expected to read (solar) time properly. With some dials, such as equatorials, it is easy to introduce small construction errors which require a minor corrective tilting north/south or east/west during set-up, in addition to the customary clockwise/counterclockwise alignment. It was to correct this type of set-up that I wrote SundialAlign.exe, a freeware that takes interprets three daytime readings of a sundial, and calculates how the dial must then be adjusted to correct its alignment. The method it uses works best near either solstice (such as now), and is worthless near the equinoxes. Errors from to sundial alignment are magnified most at the solstices, and least at the equinoxes.
Bill Gottesman www.precisionsundials.com In a message dated 6/16/2003 4:23:40 PM Eastern Daylight Time, [EMAIL PROTECTED] writes: > > Does anybody agree with my theory? Is there a best time for setting > sundials? > -
