John Carmichael wrote: > I've been thinking that, using plywood, I could cut a curved section (20 > degrees) of a protractor's scale and tying both ends to the dial's center > (w/ two long non-strechy strings), I could rotate this pie-shaped thing, > like a drawing compass, about the center to mark the timeline angles. Tom > Semadeni did something similar in builing his "Celeste". This rotating > protractor section would be very simple and probably easier than the > coordinate method. No problems with perpendiculars and measuring tape > (which takes two persons). Also the marking of each time lime > only involves one measurement instead of two.
It still sounds like a lot of work. As long as you're only laying out hour lines, not doing something more difficult like drawing analemmas or setting up an analemmic dial, why not do this: With a tape measure or non-stretchy string draw a (half) circle of known radius centered on the base of the gnomon. Each hour line should intersect this circle in a particular point. Calculate the distance from these points to the intersection of your north-south line with the circle. Using a tape measure pegged to the intersection of the north-south line with the circle, measure out and mark the distances to the points on the circle. Connect the dots. Voila! --Art Carlson
