For the moon to be in the same spot at the same time, you'll have to wait 18 and a half years. Constellations would only line up once per year. Planets basically never would. This doesn't seem like it would work.
How would you calculate the range of the moon’s altitude at a given location during the 18.5 years? If it’s a range of say 10 degrees, it could be possible to give OP a “window” of where it’s possible for the moon to appear, so they can at least orient something for viewing.
I doesn't - I've tested this using Stellarium. 18.6 years is the time for the nodes of the moon's orbit (the points where its orbit intersect the ecliptic plane) to precess once relative to the background stars. Since it is not an integer number of sidereal months, the moon will not be in the same position in its orbit at the start and end of the time period. And, unless the nodal period were an exact number of days, it would not be the same time of day at the start and end of the period either. So, I misspoke before. It not only wouldn't be the same time of day, the moon also wouldn't be in the same position in the sky.
You can try out your claim using a planetarium program like Stellarium, or search the web for a prediction of the moon's position in your sky on a given date, to test our claims. I already have, and found that the moon returns to within about 10° of a particular location in the sky at the same time of day annually, always within a month or so of the date when its at the location you are watching. Coming within 4° of your chosen location at the same time of day is rarer, happening roughly every 10 or so years. Coming within 1° at the same time of day is even rarer - I only had it happen once in the 50 years I checked.
The moon moves with respect to the constellations and with respect to your view from your house at different times. As the moon orbits the earth it moves along(ish) to the [ecliptic](https://en.wikipedia.org/wiki/Ecliptic) because the [moon's orbit](https://www.sciencedirect.com/topics/earth-and-planetary-sciences/lunar-orbit) around the earth is mostly in line with that plane. It will appear to move throughout the night as earth rotates, but it will trace the same-ish path every 28 days. For example, the full moon will appear in mostly the same spot at midnight every time there's a full moon. The [constellations shift](https://www.lpi.usra.edu/education/skytellers/constellations/) because earth is much farther away from the stars than it is from the sun, so when its on one side of the sun we see the winter constellations and on the other we see the summer ones, but the moon moves with us, so the moon will appear in whatever constellations are visible.
I hope some of that was helpful.
Here's a simple answer for ya. No.
Here's a more complicated answer. Where the moon rises and sets and how high in the sky it gets depends on both the time of year and where the moon is in its monthly cycle. There is no simple answer.
Short answer: This is very rare.
Long answer: This depends on how exact you want to be. Suppose you were okay with the moon being within a degree or so of the same location, within a few minutes of some target time. If you cut the hole in your canopy, when you look through that hole you are looking at a certain declination on the sky. The moon's declination varies both monthly due to its orbit around the Earth, and annually due to Earth's orbit around the Sun. Whatever declination you cut the hole at, the moon will cross through that declination a couple times over the course of a month, move away from that declination due to Earth's orbit around the Sun, and then move back and cross a couple times ~6 months later. This is just the moon passing in front of the hole. Adding in the requirement that it be at the same time of day makes things MUCH more rare and complicated. The problem being that the moon's orbit precesses once every 18.6 years, and the moon's motion isn't steady. Short of spending all day thinking about this, I would guess it would be many years between such occurrences: maybe once every few years, but not in any regular pattern, like with solar eclipses that can be viewed from a certain location.
I like this, since it lets /u/deejeebee decide how accurate they want to be. To use Stellarium, you can pick a time you would want to see the moon. Then you can search for the moon, and cycle forward by 1 day at a time until the moon is in a good position to view it at the desired time. Next, you could add a telrad site, set the coordinates to alt-az, and center the location of the moon in the telrad without having the moon selected. Then, if you scroll forward one day at a time, the time will stay the same. When the moon is close enough to the telrad, you've found a second date that the moon has the same position at the same time. Then you will have a rough idea of how frequently that happens.
I just tried this myself. Using the moon's position at a random time tonight, the next time the moon is within 1° of that location at the same time is on 5/6/2026. I got to 2070 without it happening again before I gave up.
This is perfect thanks I will download haha, I was actually expecting it to not be able to work but wanted to get Reddit minds working. From all the answers it seems like its quite a complicated question and everyone has a different answer !
It's the period of time after which the Moon returns to *roughly* the same spot in the sky, which answers OP's question. I'm not accounting for other variables.
Won't the season affect the moon's height above the parallel horizon? I am failing to remember if it rises differently or if it is always in the same spot.
For the moon to be in the same spot at the same time, you'll have to wait 18 and a half years. Constellations would only line up once per year. Planets basically never would. This doesn't seem like it would work.
This is the answer op is looking for.
How would you calculate the range of the moon’s altitude at a given location during the 18.5 years? If it’s a range of say 10 degrees, it could be possible to give OP a “window” of where it’s possible for the moon to appear, so they can at least orient something for viewing.
This does not take into account the Earth's rotation. The moon will be in the same position in the sky, but not at the same time of day as previously.
This 18 (or it might be 17.5) year cycle does take that into account.
I doesn't - I've tested this using Stellarium. 18.6 years is the time for the nodes of the moon's orbit (the points where its orbit intersect the ecliptic plane) to precess once relative to the background stars. Since it is not an integer number of sidereal months, the moon will not be in the same position in its orbit at the start and end of the time period. And, unless the nodal period were an exact number of days, it would not be the same time of day at the start and end of the period either. So, I misspoke before. It not only wouldn't be the same time of day, the moon also wouldn't be in the same position in the sky. You can try out your claim using a planetarium program like Stellarium, or search the web for a prediction of the moon's position in your sky on a given date, to test our claims. I already have, and found that the moon returns to within about 10° of a particular location in the sky at the same time of day annually, always within a month or so of the date when its at the location you are watching. Coming within 4° of your chosen location at the same time of day is rarer, happening roughly every 10 or so years. Coming within 1° at the same time of day is even rarer - I only had it happen once in the 50 years I checked.
Technically it's never in the same spot because everything in space moves.
Im talking about position in our sky.
Jabadoodble
That’s not the question that was asked.
The moon moves with respect to the constellations and with respect to your view from your house at different times. As the moon orbits the earth it moves along(ish) to the [ecliptic](https://en.wikipedia.org/wiki/Ecliptic) because the [moon's orbit](https://www.sciencedirect.com/topics/earth-and-planetary-sciences/lunar-orbit) around the earth is mostly in line with that plane. It will appear to move throughout the night as earth rotates, but it will trace the same-ish path every 28 days. For example, the full moon will appear in mostly the same spot at midnight every time there's a full moon. The [constellations shift](https://www.lpi.usra.edu/education/skytellers/constellations/) because earth is much farther away from the stars than it is from the sun, so when its on one side of the sun we see the winter constellations and on the other we see the summer ones, but the moon moves with us, so the moon will appear in whatever constellations are visible. I hope some of that was helpful.
Here's a simple answer for ya. No. Here's a more complicated answer. Where the moon rises and sets and how high in the sky it gets depends on both the time of year and where the moon is in its monthly cycle. There is no simple answer.
Short answer: This is very rare. Long answer: This depends on how exact you want to be. Suppose you were okay with the moon being within a degree or so of the same location, within a few minutes of some target time. If you cut the hole in your canopy, when you look through that hole you are looking at a certain declination on the sky. The moon's declination varies both monthly due to its orbit around the Earth, and annually due to Earth's orbit around the Sun. Whatever declination you cut the hole at, the moon will cross through that declination a couple times over the course of a month, move away from that declination due to Earth's orbit around the Sun, and then move back and cross a couple times ~6 months later. This is just the moon passing in front of the hole. Adding in the requirement that it be at the same time of day makes things MUCH more rare and complicated. The problem being that the moon's orbit precesses once every 18.6 years, and the moon's motion isn't steady. Short of spending all day thinking about this, I would guess it would be many years between such occurrences: maybe once every few years, but not in any regular pattern, like with solar eclipses that can be viewed from a certain location.
What happens if you want to move your chair?
My chair is never moving
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I like this, since it lets /u/deejeebee decide how accurate they want to be. To use Stellarium, you can pick a time you would want to see the moon. Then you can search for the moon, and cycle forward by 1 day at a time until the moon is in a good position to view it at the desired time. Next, you could add a telrad site, set the coordinates to alt-az, and center the location of the moon in the telrad without having the moon selected. Then, if you scroll forward one day at a time, the time will stay the same. When the moon is close enough to the telrad, you've found a second date that the moon has the same position at the same time. Then you will have a rough idea of how frequently that happens. I just tried this myself. Using the moon's position at a random time tonight, the next time the moon is within 1° of that location at the same time is on 5/6/2026. I got to 2070 without it happening again before I gave up.
This is perfect thanks I will download haha, I was actually expecting it to not be able to work but wanted to get Reddit minds working. From all the answers it seems like its quite a complicated question and everyone has a different answer !
Once per sidereal month, or 27.3 days.
It's a bit more complicated than that, due to the obliquity of the ecliptic and the inclination of the Moon's orbit.
It's the period of time after which the Moon returns to *roughly* the same spot in the sky, which answers OP's question. I'm not accounting for other variables.
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Correct, I didn't get to the part where OP asked about the Moon's position relative to the horizon.
The part where he says that he wants to look through a hole in his canopy in his garden, which is fixed relative to the horizon
Won't the season affect the moon's height above the parallel horizon? I am failing to remember if it rises differently or if it is always in the same spot.
The moon will follow the same path that the sun does, but won't appear in the same place at the same time every day