Seattle's long and rarely sunlit winter has begun in earnest. I'm experimenting with building dials and want to test the ability of different gnomon designs to cast shadows.
Does anyone have ideas on building simulated sources of sunlight? I'm guessing a reasonable approximation is to simply put a bright light in a tube, and choose the appropriate tube diameter and distance from the dial so that the angular size appears near 32 minutes. Or do you need lenses to make the light appear more parallel? Maybe my old slide projector could do the trick with some modifications. The well-stocked gnomonicist should probably have such a tool regardless of available sunlight! This is especially the case if the person's dials of choice include those that are sensitive to seasonal variations. Thanks, Tom
