Just to clarify what’s going on for the benefit of others:
At USA/Europe latitudes, the Sun follows a path that is “tilted” toward the S as it passes from roughly E in the morning to roughly W in the evening. But due to the tilt of the Earth’s axis of rotation, it is much higher in the S sky during the long days of summer, and lower in the S sky during the short days of winter. This means that the direction of sunrise and sunset also varies considerably during the year.
Spring/Fall equinoxes: sunrise due E, sunset due W
Winter: rises late in SE, remains low in S part of sky, sets early in SW
Summer: rises early in NE, passes thru E and high into S part of sky, sets late in NW
Now, the Moon. The Moon orbits roughly around the equator, i.e. in the same plane as the orbit of the Earth around the Sun (there’s actually a difference of about 5 degrees). So like the Sun, the risen Moon is in the S part of sky at USA/Europe N latitudes.
At a new Moon, the Moon is in the same direction as the Sun, and if you can see an illuminated sliver it it will follow roughly the same seasonal pattern as the Sun described above. Many people don’t realize that the reason you cannot see the new Moon is not just because it’s not illuminated. It’s also because it rises and sets at roughly the same time as the Sun, i.e. it’s “up” during the day.
At a full Moon, the Moon is opposite the Sun. That means it rises in the evening and sets in the morning, and is visible all night. But the additional subtlety that @commasense is noticing is that the full Moon in winter has the same path as the Sun in summer. In winter the sun rises SE, sets SW, and is “up” for only about 9h. Whereas in winter the full Moon rises NE, sets NW, and is “up” for about 15h, similar to the Sun in summer.
In specific, the Islamic Calendar uses the sightings of hilal (Arabic for crescent moon) as the indicator of when a month starts. But the sighting has to be from Mecca, not just anywhere. I would guess without googling that they have an official in Saudi Arabia whose job it is to make that sighting.
But the amateur astronomers I read about in S&T will make their observations from anywhere. They may make calculations that there will be an especially early sighting from a certain latitude and/or longitude on a specific date and go there.
For sure - the slight inclination in the plane of orbit of the Moon vs the ecliptic is only 5 degrees out of a maximum possible 90 degrees, so think of it as around 5% - it doesn’t make that much of a difference. The major difference for the Moon of course is that it varies on a monthly cycle rather than the Sun’s yearly cycle.
At very high latitudes deep in the Arctic or Antarctic circle the Sun is up perpetually for months in summer, and down perpetually for months in winter. For a few days each month, the new Moon does the same thing as the Sun; and for a few days each month the full Moon does what the Sun would do in the “opposite season”.
So at very high latitudes a winter new Moon is down perpetually for several days in the month; a winter full Moon is up perpetually for several days. A summer new moon is up perpetually for several days each month; a summer full Moon is down perpetually for several days.
The page I linked has a great graphic that shows what parts of the globe are illuminated by the Moon (and Sun) on any given date and time, it makes it easy to visualize if you advance it hourly.
At the tabs near the top you can move from Moonrise & Moonset to other options.
The table below defaults to the current month, you can change it.
In Dec 2021 the Sun never rises for the entire month.
With new Moon on Dec 4, the Moon never rises from Dec 2 to Dec 9.
With full Moon on Dec 19, the moon is up perpetually from Dec 15 to Dec 24.
I have realized that what I wrote here is confusing. If the Earth’s axis of rotation were not tilted, the Sun would still be in the S part of the sky. The tilt in the axis of rotation only causes the seasonal variation in how high or low in the S sky we see the Sun.
This rewrite of that paragraph would be better:
At USA/Europe latitudes, the Sun follows a path in the S part of the sky as it passes from roughly E in the morning to roughly W in the evening. But due to the tilt of the Earth’s axis of rotation there is seasonal variation. It is much higher in the S sky during the long days of summer, and lower in the S sky during the short days of winter. This means that the direction of sunrise and sunset also varies considerably during the year.
Perhaps a mod would edit the paragraph in the original post and then delete this post to avoid confusion?
It makes enough of a difference to keep it from aligning with the Sun very often. If it had no ecliptic deviation, there’d be an eclipse every month (though they still may be annular eclipses, based on where things are in their eccentric orbits). Of course, these would only occur within the tropical latitudes of 23n to 23s.
Yes, that’s certainly true. But the 5 degree difference is small enough that if you build a mental model of the Moon as though it’s in the same place as the Sun at new Moon and opposite the Sun at full Moon, that gives you a fairly accurate basic idea of how the Moon will behave in terms of the direction and timing of moonrise and moonset at different latitudes.
If you click on the link and are logged into FB it would show you a picture of the cycle of the moon through 28 days, taken from the same place at the same time.
Same place, couldn’t be the same time. When the moon is full, it’s visible at midnight. When it is new, it is directly below your feet at midnight. If you pick a particular time to look at the moon, about half the days it will be below the horizon at that time.
