Some more moon questions, if I may. Don’t think they’ve been answered before.
How do moonrise and moonset times vary? Does the moon always rise around sunset and set around sunrise?
What I’m wondering is: is it possible to have moonrise at say, 10 am and moonset at 4 pm so that we don’t see the moon that night? Since the moon’s orbit and Earth’s rotation aren’t in sync, sounds like it could be possible.
How much is the difference and wobble between the Earth’s and moon’s rotation? Does the moon’s path across the sky vary a lot, say, like the Sun’s? Is the period a year (not likely), a lunar cycle, or something else since it depends on the rotation of both?
If I’m looking for the Moon at a certain time, what software is best to use to find its position?
Given the 5 degree difference between the moon’s orbit and the Earth’s (+/- 5 degrees north or south), and also given the fact that the moon is about half-a-degree in size (as is the sun), then I’d predict that we would see at least a short-duration partial solar eclipse somewhere on the Earth once every 6-8 lunations or so, which, checking Wikipedia’s eclipse schedules, seems to be about right. The moon just has to overlap the sun’s disc going north or south to qualify as an eclipse, so there’s a maximum of one and a half degrees worth of leeway for the moon to intersect the sun. 1.5 out of 10 is about 1 out of 7; however any given spot on the Earth won’t be seeing these eclipses 1 out of 7 times, because typically the penumbral shadow of the moon (which generates the partials) will only follow a fairly narrow path across the surface of the Earth.
Feel free to clarify or render more precisely my estimates.
A completely full moon will be at its highest at 12 midnight. A completely new moon will be at its highest at 12 noon. So no, the moon doesn’t always rise around sunset.
Elaborating: Only when the moon is full is it opposite the Sun in the sky, when you’d expect one’s rising to coincide with the other’s setting. At new, they rise and set together. Any other time, they’re some interval apart, and the interval can be anything greater than zero and less than twelve hours.
I’m sometimes amazed at the things I think everyone knows, but I guess some people just don’t pay attention to. Just last Friday, my wife saw the full moon rising about 8:30, and said how it would be really pretty when we were to be boating on the lake the next night. I pointed out that it would be fairly late for that to be, because 1) the moon wouldn’t be rising the next night until close to 9:30, and 2) you’d need to wait a couple of more hours for it to be sort of overhead and lighting things up.
She questioned the bit about rising the next night about an hour later - she had just never noticed that the moon rises later every day. And she’s 51 years old! And married to me!
