Length of time between moonrise and moonset

Jan 22, 2020
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Hi - I'm pretty sure I understand the phases of the moon and why the moon rises later by approximately 50 minutes each day. However I'm struggling to see why the length of time between moonrise and moonset varies so much. For example at my location in Scotland on Wed 22nd Jan Moonrise is at 0703 and Moonset is at 1500 which is 8 hrs 3 minutes. But a few days later on Tuesday 28th January Moonrise is at 0940 and Moonset is at 2031 which is 10 hrs 51 minutes. Also, by my reckoning, adding 50 minutes each day from the 22nd to the 28th means that moonrise should be approximately 1200 hrs, not 0940. I'd be grateful if anyone could explain this. Thanks
Dec 30, 2019
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The Moon's altitude (measured midway between moonrise and moonset) can vary as much as 12 degrees, so at its highest, you will have longer intervals between moonrise and moonset, and when lowest, the intervals will shorten.
Dec 11, 2019
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Great question I’ve often wondered the same thing watching from the upside down in Australia. I hope someone can be helpful.

:D Atleast you are having Summer there though lucky.lol!

I have no clue about the question. Although if you were in space I don't think you would see the moon setting or rising.lol! So if this is all an optical illusion on the Earth it must have to do with the tilt of the Earth and the spin. I do know the days are getting longer from the point of the Winter Solstice. More sunlight is coming to the northern hemisphere because the northern hemisphere is tilting closer to the sun while now your hemisphere is moving away and your days getting shorter.
It's a complicated question.
The Moon orbits the Earth. The Earth in it's turn orbits the Sun and the Sun orbits the Galaxy center. Orbits are only approximately circular. They are actually ellipses. Moon and Earth are both rather circular in their orbits, but not actually circles.
In a circle, the outer edge of the circle always has a constant distance from the center or focus. In an elipse, the outside always has a distance from the two focii that is a constant, but it is the sum of the two distances that is the constant.
Then, where you are on the Earth matters. Plus, the Earth is tilted with respect to the Moon and the Sun. Your specific latitude also matters, as you see the moon from a position that moves relative to the actual position of the Moon during the day/night. But the Moon has also moved during that time, as has the Earth. Then again, just how your part of the Earth is tilted as you look at the Moon varies with the seasons as well.
This just gives some of the considerations. To really answer the question would take 3D Trigonometry and some Solid Geometry. Those two subjects come together in Analytic Geometry, which is covered in second year Calculus and which is beyond anything that belongs on this website.
I would suggest you write off to a planetarium. Illustrating things like this is part of why they exist. New York has a good one, Neil DeGrasse Tyson runs that one and has a good reputation.


"Science begets knowledge, opinion ignorance.
Are you taking into account the shape of the rise/set v time graph over the year?
If you start at the top, summer solstice, days are longest. Change ln length of day is slowest but, as time passes the day shortens more quickly. At equinox change in length is maximum. Towards winter solstice change in length of day slows down until it flattens out towards the solstice.
This is repeated as I am sure you can work out back to Spring Equinox and then to Summer Solstice.
I hope this helps.
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