Perspective/geometry/celestial mechanics question that's baffled me for years. I took this photo tonight ~1 hour after the sun set. Camera perfectly level. Why, if the sun has set toward the right of the frame, is the moon shadow's axis of symmetry still inclined *upward*?
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Replying to @stshank
I think: 1. If the moon were precisely on the horizon (0° elevation), this wouldn't happen. 2. If the moon were straight above (90° elevation), you'd see this if the sun had set >90° right of where you'd aligned (and then elevated 90°) your camera, but not if <90° right 1/2

Sep 20, 2018 · 11:44 PM UTC

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Replying to @davidbaron @stshank
3. When the moon is at some intermediate elevation (between 0° and 90°) then the threshold for this effect would increase from >90° to the right (at 90° elevation) to higher angles as the moon gets lower. Maybe it doesn't hit 180° right until 0° elevation? Not sure yet. 2/2
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Also, per timeanddate.com/sun/usa/san-… sunset yesterday in SF was at 272° and per timeanddate.com/moon/usa/san… moonrise was at 115°. So the sunset was 157° to the right of moonrise, though that angle difference would be smaller 3 hours after moonrise, but probably not by a huge amount.
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Replying to @davidbaron
This is my guess, too, but I wasn't patient enough to wait several days for posting, especially because I'd hoped Twitter would do the hard analysis work for me. :)