This is my hypothesis.
The larger crescent was the normal and direct view of the Moon.
Off the line of sight, there was a high layer of atmospheric vapour in the shape of a rough lens (like a lens shape cloud). This focussed the incoming crescent image as a smaller image onto a less dense layer of vapour below but off the line of sight. A fluke of shape and position of atmospheric vapour.
The smaller crescent should have been less defined.
Regards, Rob.
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