Here's the second thing I learned from photographing the moon last week, and this is visible in this set of photos here, is that the altitude of the moon in the sky changes when the moon as at the same bearing (direction on the compass) on each of the nights. That is, the arc that the moon follows across the sky each night is different. At this point in the lunar cycle, with each successive night the moon travels a slightly lower arc across the sky. I haven't the foggiest why this is, but it indicates that the moon's orbit around the earth isn't fixed. So the sun does this on an annual cycle (sun is lowest in the sky at Winter Solstice, highest at Summer Solstice), but the moon appears to do this on a lunar cycle. And why doesn't the moon just slip out of earth's gravitational field if its rotational axis wobbles around so much? And why does the moon always face us from the same direction?