Questions tagged [the-moon]

Questions regarding Earth's only natural satellite. For questions about the natural satellites of other planets, use the tag [natural-satellite].

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How to get the right ascension of the Moon?

Is there any approximate way to calculate the right ascension of the Moon? I already got declination but still, need the right ascension to calculate the final position of the moon. Thanks for all ...
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2 votes
0 answers
32 views

Finding out the distance to the moon from Parallax

How could I determine the distance from the Earth to the moon by using the method of simultaneous parallax? I know the right ascension and declination as seen from two different points on earth. I ...
1 vote
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From a given latitude on Earth, how to calculate the number of days in a year when the moon is lit on the bottom?

From a given latitude on Earth, is it possible to calculate the number of days in a year when there is a wet moon , that is when the moon is lit on the bottom? If, for example, I want to do the ...
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4 votes
1 answer
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How exactly is defined elevation on the Moon?

In a recent image by Pavel Gabzdyl, the highest (+10.7 km) and lowest (-9 km) points on the Moon are marked. Detailed info about these extremal points can be found at the following links: Highest ...
1 vote
1 answer
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Python Program for Synodic months

I am trying to make an astronomical program for celestial bodies in our solar system (and beyond!). However I want it to show how many Synodic months since New moon. Example: Since last 2022 there ...
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0 answers
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Could we by ordinary mining activities, affect the Lunar orbit? [migrated]

In The Time Machine (Guy Pearce version), they manage to literally break up the Earth's moon with obviously disastrous results and I believe they were just building underground structures. I am ...
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1 vote
1 answer
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How long before two sidereal months start on the same lunar phase?

I was reading about the difference between the sidereal and synodic month when I started to wonder how many sidereal months need to pass before you get two that start on the same part of the synodic ...
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17 votes
6 answers
4k views

How do we know the moon is smaller than Earth?

The moon is smaller than the Earth, but how do we know that (without the use of modern technology)? To be more specific, how can we show that the moon is smaller than the Earth (smaller diameter) with ...
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3 votes
1 answer
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Metonic cycle observation & display [closed]

I'm unable to locate physical display observatories for the 19 year Metonic cycle. How do I display this information & calendar detail on a concrete floor near the tropic of cancer? I seek a floor ...
3 votes
1 answer
93 views

New moon rise same spot on horizon as sunrise, almost same time [closed]

I witnessed the new moon rise just ahead of a sunrise at the very same spot on the horizon. How often could I plan on looking for that occurrence again?
3 votes
1 answer
114 views

How dark is the side of the Moon facing away from the Sun? ( I don't mean the far side)

Remember, the actual "dark side" of the Moon is not the far side, facing away from us that we can't see, but rather it's the side that faces away from the Sun that is illuminating it.​
8 votes
2 answers
281 views

Trying to understand lunar phases

Complete novice here. I'm trying to understand what appears to be two approaches to quantifying lunar phases. Have I got this right? Named lunar phases can be understood as the Moon's ecliptic ...
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1 vote
1 answer
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How do times of lunar standstills vary over time? If we folded them back into a lunar month plot, would they have "prograde and retrograde motion"?

The recent question Are lunar phases and lunar standstills in sync with each other? brought me to a standstill because I don't fully know what a lunar standstill is. It's one of those words like "...
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7 votes
1 answer
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Are lunar phases and lunar standstills in sync with each other?

Do either of the standstills (N/S) coincide with full/new moon? If yes - what is the relationship? If no - what factors impact the relationship between the two?
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3 votes
1 answer
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What experiments can be performed during a solar and lunar eclipse respectively?

As an amateur astronomer, I intend to perform a few simple experiments during total solar and lunar eclipses. However, I am not aware of all the parameters that can change during these eclipses and ...
1 vote
0 answers
133 views

JPL Ephemeris or Skyfield - how to get moon phase percentage (not illumination percentage)

I know how to use JPL's Horizons to get moon illumination percentage but I noticed that even at new moon, the illumination never goes to zero: ...
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3 votes
2 answers
103 views

Why doesn't lunar perigee always occur in the same lunar phase?

If the phases of the moon and the moon's perigee are just dependent on the point that the moon is in through it's orbit, why can perigee happen at different phases of the moon? My thinking is this: ...
2 votes
0 answers
126 views

tool to calculate moonrise/moonset and moon phase for any date for any location

I have googled for such a solution but I have not found anything substantial: I found one website but it was someone's side hobby so my confidence in it is low. Thankfully, I have discovered ...
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2 votes
1 answer
67 views

How can I compute the shape and orientation of the crescent for a given time and geographic location using data from the JPL Horizons?

I can compute the following data for the Moon for a given time and geographic location using the JPL Horizons system: Apparent RA & DEC Apparent azimuth & elevation (AZ-EL) Target range & ...
-4 votes
1 answer
210 views

Help me better understand how the plane of Moon's orbit around Earth behaves

Is the plane in which Moon orbits around earth, inclined with respect to earth's equatorial plane? If yes, is it constant or does it change with time? If it changes, how much time does it take to make ...
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-1 votes
1 answer
67 views

Tidal locking of Moon [duplicate]

Since our Moon is tidally locked with earth, we always see only one side of the Moon. In such a case, how and when did mankind first realize that the Moon is also revolving around its own axis? or for ...
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4 votes
1 answer
281 views

Bolometric correction of the full moon

Now I am solving the problem about the transition from $V$ (= -13 in 400-700nm) to $m_{Bol}$. V is the full moon's apparent magnitude in 400-700mm(i.e., visible light), and $m_{bol}$ is the bolometric ...
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4 votes
0 answers
155 views

How to measure the latitude of the moon?

In the geocentric solar ecliptic (GSE) system of coordinates, the position of the Moon is described by its longitude and latitude. The former is, with great accuracy, the angular distance between the ...
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-5 votes
1 answer
233 views

Why is the moon tidally locked with the earth?

Why the moon is tidally locked with the earth? What is the reason for the tidal locking of the moon with the earth? What causes tidal locking?
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2 votes
1 answer
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Lunar Librations and Subsolar Point in Matlab

So I have been trying to write a program to generate the latitude and longitude of the lunar subsolar point in Matlab. I have the ephemeris data from aero toolbox, but I can't seem to get values that ...
2 votes
2 answers
104 views

Waning gibbus moon tilt

Can anyone explain why on the 14 Oct 2022 at 7.00 UTC at location (Lat 52.339 Long 0.419)does the waning gibbous moon (Alt 39º) appear to be illuminated from a different direction, i.e. slightly ...
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2 votes
0 answers
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Besides Luna, are there any models of how moons become spherical and round?

Question Given the theorized exceptional formation of Luna, (Giant-impact Hyphothesis, Wikipedia), are there any similar animated models of how the other, much smaller, moons in our solar system ...
10 votes
2 answers
209 views

How do we know the hydrocarbon lakes on Titan are actually liquid?

Cassini failed to detect any waves in the seas/lakes it observed, despite winds of 72 km/h (45 mph) being present on Titan which are able to create "sand" dunes from frozen particles, and ...
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16 votes
2 answers
4k views

How does the earth cast straight and reversed shadows on the moon?

When the Earth regularly casts a shadow on the moon, why does the shadow progress from circular to a straight line and then to a reversed circle? Since the earth is a sphere, shouldn't it cast round ...
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1 vote
1 answer
56 views

Sky viewer from the moon

Is there any app or website that is able to view the sky from the moon? It would be like https://www.timeanddate.com/astronomy/night/ except that it is viewed from ...
9 votes
3 answers
3k views

What is the difference between New Moon day and Lunar Eclipse?

A lunar eclipse occurs when the Earth is in between Sun and Moon. OK, I understand this (see diagram from Nasa). A new moon is also when the Earth is in between Sun and Moon. So, why are they not the ...
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1 vote
1 answer
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Can the Celestron Powerseeker 127EQ observe the moon during day time?

I am able to find the moon with the finder scope during the day. However, when I use my 20mm lense, it seems like I am unable to focus the moon at all. Is there a fix to this?
2 votes
2 answers
153 views

The exact definition of lunar eclipse

I was finding the definition of the lunar eclipse (in which the earth blocks the sunlight that comes to the moon), and I have found that it could be defined differently. Definitions of lunar eclipse ...
15 votes
3 answers
6k views

What is the **actual** average distance of the Moon from Earth?

The Moon orbits Earth at a semi-major axis of 384400 km, with its periapsis being 363300 km and apoapsis being 405500 km. (All figures from this NASA fact sheet.) If the Moon orbited Earth at a ...
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1 vote
3 answers
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Is there a Lagrange point between the earth and the moon?

Is there a Lagrange point between the earth and moon where a space station could sit forever without orbiting around either? Just curious, but it seems like a place like that would be perfect for ...
1 vote
1 answer
179 views

How much energy to shorten a synodic month by about 1.56%?

Suppose the moon underwent a single, massive, large-object bombardment event. About what number (or range) of about what mean mass of objects could shorten the synodic month by about 1.5633%? (Assume ...
1 vote
1 answer
85 views

Lunar sky brightness

Looking at the report "The Measurements of Sky Brightness on Lunokhod-2"1, I read that the day time visible light sky brightness was so large that it was off the scale. Unfortunately I have ...
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5 votes
1 answer
316 views

Is there a word or short phrase that denotes the apparently moving part of the lunar limb?

Between new moon and full moon, the moon's disc as viewed from the earth is bounded by a semicircular arc on its right and an arc on its left that moves to the right until at full moon it forms the ...
user avatar
2 votes
1 answer
81 views

How to explain this elongation frequency diagram between the Sun and the Moon

Intrigued by my recent question about the average angular distance between the Sun and the Moon, I tried to inquire this little more in attempt to find the source of the asymmetry. Basically I have ...
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5 votes
1 answer
113 views

If the Earth became tidally locked with the moon, would that last forever?

If the Earth and the moon became tidally locked, would this last theoretically forever (assuming no external gravitational force modifies their orbits, for example, ignoring the effects caused by the ...
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3 votes
2 answers
2k views

Is it possible to block the surrounding light in a solar eclipse if we made the moon bigger or closer to the earth?

Is it possible to block the surrounding light in a solar eclipse if we made the moon bigger or closer to the earth? In an eclipse, you always see a ring of light surrounding the moon, but I am ...
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1 vote
2 answers
150 views

Earth’s rotation speed vs rate of lunar cycle

Hypothetical Question If the earth’s rotation slowed down to align to the lunar cycle so that the orbital period began and ended at the same lunar phase, what other things would result? For example, ...
5 votes
2 answers
378 views

What is the average angular distance between the Sun and the Moon?

Naturally we would expect the average angular distance(*), to be exactly 90°, for although the Moon is not running in uniform speed (or rather, to be more precise, the relative angular speed of the ...
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9 votes
3 answers
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The moon in the first phase visible in the sky is tilted

I never noticed it before that moon I see in the sky is tilted. Does the tilt of the moon in the sky indicate the direction of the Earth's axis and direction of Earth's rotation around the sun?
18 votes
3 answers
3k views

What is this 877-year cycle in the orbits of Jupiter & Saturn, and this multimillion-year cycle in the lunar orbit?

The book The Theory That Would Not Die (by Sharon Bertsch McGrayne, 2011) states the following on page 28: He [Pierre-Simon Laplace] used other methods between 1785 and 1788 to determine that Jupiter ...
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7 votes
1 answer
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Earth-Moon Barycenter Perihelion

I am trying to implement an algorithm I created to get the sun rise, transit and set accurately, but in order to do that I need to get the Earth-Moon barycenter (EMB) perihelion, and not the Earth ...
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17 votes
3 answers
3k views

Can the Earth be seen from the moon when we have a total lunar eclipse at the perigee?

We know that the Moon doesn't have an atmosphere; thus the sky is seen dark. Also, from this question, the angular diameter of the Earth viewed from the Moon is a bit bigger than $2^\omicron$ at the ...
15 votes
6 answers
8k views

How is this picture of the moon possible?

I need help understanding this images I personally took. If the phases of the moon are determined by the position of the earth, moon & sun. Then how is the moon a crescent while it is rising in ...
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6 votes
2 answers
774 views

The moon rises at a different time each day, but that difference changes. Why?

Let's say the moon rose at 5pm yesterday and 5:30pm today. The difference is 30 minutes – but that difference changes from day to day and can be anywhere between twenty-some to seventy-some minutes. ...
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1 vote
1 answer
252 views

Moon path diagram for a location

There are a lot of sun path diagrams online (i.e. https://www.gaisma.com/en/location/seattle-washington.html), but I'm struggle to find a moon path diagram. Is that called something different? I'm ...
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