On Wed, Jun 25, 2008 at 11:01 AM, Chris Lusby Taylor <[EMAIL PROTECTED]> wrote: > Very neat John! > > But I don't think it works. Not even if south-facing. > > The problem is that you are halving the angle through which you turn the > dial. That affects the geometry of the elliptical dial. You can't just > renumber the hour marks. The sun's azimuth (measured from south) at 2pm is > not twice the azimuth at 1pm. > So, I'm pretty sure you can't just take an analemmatic ellipse, reverse and > renumber the hours. But maybe there is a shape, perhaps a different ellipse, > that would work. You might well have to change the date scale as well.
John's neat idea rearranges things as if the Sun during the day moved only up and down along the celestial meridian while the missing azimuthal motion is done by the sundial itself. As Chris points out, the dial cannot be rigidly fixed to the mirror since the mirror only moves through half the required azimuth. So one way to fix this small problem is to rotate the sundial twice as fast as the mirror - perhaps have them connected by some simple 2:1 gearing mechanism. -- Jan --------------------------------------------------- https://lists.uni-koeln.de/mailman/listinfo/sundial
