Hello John D. In answer to your challenge, I would pick a "Singleton" type dial over the Swensen dial because:
1) A Swensen dial can only give accurate times on the hour. For times between the hour you need to guesstimate. 2) A Singleton time line is easier to read since the analemma is unfolded. Smaller increment time lines can easily be drawn onto a Singleton, but if more analemmas are added to a Swensen, then they begin to overlap and reading would become even more difficult. 3) Singleton sundials avoid the Swensen's analemma date confusion. 4) The Swenson's nodus has two support rods which create unnecessary and confusing shadows not present in a Singleton. 5 )Even if the Swensen dial were horizontal instead of vertical, It would be impossible to show early morning and late afternoon hours on a Swensen dial because the analemmas would be prohibitively long. A Singleton does not have this considerable limitation. 6) The only drawback I really see with a Singleton is that it suffers from time line compression on the inner rings. This problem might be solved by making the dial larger (which would also increase its precision). Thumbs up on Singletons! John Carmichael Tucson Arizona John Davis wrote: >Hi all, > >I have a question/challenge to all you sundial designers: what is the most >accurate design for a Standard Time dial? > >The reason behind the question is to find a way to stop members of the >public looking at a public dial, inspecting their watches, and concluding >that dials never tell the right time! > >The criteria for the dial are, in my opinion: > >a) it should tell Standard Time, (or possibly Daylight Saving Time - BST in >the UK) >b) it should be in a fixed location >c) it must have no moving parts (which rules out adjustable equatorials and >changeable gnomons etc) and > should be as physically robust as possible. >d) it must not require reference to a separate table or computer program eg >to get an exact declination for the sun. > All data must be built into the dial plate. >e) the "accuracy" should be interpreted as the mean error for the hour >lines 3 hours either side of noon (or 12:00) for the years 2000 to 2050. > >As a starter, the "Singleton" dial recently discussed here would seem to be >a reasonable candidate. It's main limitation, common to all dials which >incorporate an EoT correction, is that it is drawn for a some MEAN EoT >curve, and no allowance is made for the leap year cycle and the other minor >variations. Is there some geometry of dial plate and style which minimises >the time error caused by small year-to-year variations in the mean daily >declination? If this is achieved, then the small change in the EoT over a >single day may be allowed for. > >There is no prize for the competition, but I promise I will build a physical >example of the best suggestion, and share it with the list! > >Happy designing, > >John >---------------------------------------------------------------------------- >---------------------------------- > > >Dr J R Davis >Flowton, UK >52.08N, 1.043E >email: [EMAIL PROTECTED] > > >
