Did you see the link to that old book? There's an image in it that is an exact duplication of this pattern.
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Yes, I did (it was a great find!) and it backs up my initial assertion. It appears, at least from my perspective, to be similar to lunar parallax which was first detailed in that book, the Almagest, though its likely showing whatever spherical object is above Earth and its movement as Earth spins with it remaining overhead.