[EMAIL PROTECTED] (John Carmichael) writes: > >... Why not follow John Singleton's notion (p. 51, BSS Journal > > for Feb 2000) and use your normal taut wire pole style? > > > >Have I missed something in the discussion? > > Maybe we all have. I think John Singleton's azimuthal will not work (except > at noon, sunrise and sunset). I know this is a rather bold statement to > make, but I think there is a general misconception that azimuthal dials can > work with either a vertical gnomon or a polar axis gnomon as was originally > suggested in an earlier discussion. This has always bothered me because it > seemed impossible. If a polar axis works, then it would certainly solve the > gnomon height problem. > > Rather than speculate, I did a simple experiment. Using a Spin drawing of an > azimuthal for my location and an icepick for the gnomon, I quickly found out > that the dial worked correctly when the icepick was vertical and became > progressively worse as I tilted it towards the celestial pole.
A dial with date rings (neither "azimuthal" nor "Dali" is quite the right name) can be designed for any gnomon, in particular for either a straight vertical gnomon or a straight polar gnomon, but any given dial plate will only work with its own gnomon. Your mistake was trying to use a "vertical drawing" with an polar gnomon. --Art
