Quote:
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Originally Posted by Jeff Root
I calculate that, when the angle from Sun to observer to Moon
is 90 degrees, the difference between the Moon's terminator
and a ball's terminator will be between 0.1 and 0.2 degree,
measured from the center of each.
-- Jeff, in Minneapolis
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That's not much of a difference. The eye would never discern that difference. It would even be difficult in a photograph to measure a difference as small as 6-12 arcminutes.
As far as the eye can tell, the ball in front of the Moon has the same phase as the Moon.
What were you using as the ball / eye distance? Does this difference increase or decrease as the Moon approaches full?
When I attempt to do the photograph I'm going to back off a bit, much more than an arm length, so I can zoom in and attempt to get the ball and Moon to be comparable sizes.