I have also considered using this type of arrangement (a "dot" on a clear pane) for several projects in the past. I wonder just how big the dot would have to be? I assume penumbral effects would be at play, and the distance to the shadow receiving surface would probably be a factor in determining the best size of dot to use?
Perhaps there is a good ratio to use for dot/disc size vs. distance to the shadow field? Perhaps some of the list members know the answer to this...
Best, Jim
We're also discussing what I call "antiaperture" gnomon sundials. These are neat. Imagine a large clear pane of clear or light colored glass on a wall. And on this glass is a small very dark dot. Instead of a hole in a wall casting a beam of light, the dark spot casts a shadow onto the sundial face. (John Davis, do you have a term for these?) Does anybody have any opinions on the practical differences of using aperture gnomons versus antiaperture gnomons? thanks John
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