Art Carson wrote: <They would not have to be more accurately aligned than the hour line itself.> <In fact, you could drill a hole in the center of each hour line and use that> <as your pinhole. You're "on the money" when the image of the gnomon> <bisects the image of the sun, regardless of where those images are > <projected.>
I agree. We are talking about very precise hour line marks, however. To be accurate to within 4 seconds of time the hole in the center of the hour line (and of course the hour line itself) must be accurate to within 1' of arc. My "free pin-hole technique" requires only that the hour line be accurate, a small advantage. Keep watching those shadows. Bill
