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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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?
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1 vote
1 answer
85 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 ...
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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 ...
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1 vote
1 answer
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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 ...
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1 vote
1 answer
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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
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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 ...
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2 votes
1 answer
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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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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
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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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2 answers
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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, ...
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5 votes
2 answers
157 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?
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18 votes
3 answers
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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
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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 ...
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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
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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
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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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2 votes
1 answer
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Earth-Mars-Moon or No Moon Barycenter Orbit Possible?

Could an object of sufficient mass deflect Mars so that it ends up stably orbiting an Earth-Mars-Moon barycenter? What would the distances eventually become between each orbiting body? What if the ...
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-1 votes
2 answers
201 views

What if Earth’s moon started rotating?

Hypothetically speaking, what might happen to Earth if one day the moon became un-tidal locked and started to rotate?
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5 votes
1 answer
43 views

When does DSCOVR see the Moon transit Earth?

In 2015, NASA published the first images of the Moon transiting the Earth as seen from DSCOVR. The text accompanying these images says such a transit would be captured on camera about twice a year. I ...
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2 votes
0 answers
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How strong is the evidence or argument for the Moon as stabilizer of Earth's axial tilt? [duplicate]

It's thought that the Moon stabilizes Earth's axial tilt, and so without it, seasons as we know them could not exist i.e. there could be extremes during periods where the tilt approaches 90 degrees. ...
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22 votes
2 answers
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What ground-based observational evidence is there that the Moon doesn't have an atmosphere?

The Moon doesn't have any significant atmosphere (surface pressure is $3\times10^{-15}$ bar). Can the absence of atmosphere on the Moon be determined with ground-based observations? When was it first ...
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5 votes
2 answers
377 views

Tips of Crescent

Can it be shown mathematically that the line connecting tips of crescent is parallel to the North-South line and the line gives latitude of the plane ( When the Moon is sufficiently close to the ...
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1 vote
1 answer
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Can I use 75mm Plano convex lens to build telescope [closed]

I want to see Jupiter with moon. So am planning to build telescope. Can I use 75mm Plano convex lens with 1000mm focal length?
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2 votes
1 answer
113 views

Sun Moon earth Angle

I want to do a theoretical prediction before trying out an experiment. I just noticed that the arc separating the illuminated side of moon and the shadowed side is an ellipse arc. So Is it possible to ...
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7 votes
1 answer
101 views

Would anything be different on Earth if the rotation of the Moon wasn't synchronous?

The Moon is in synchronous rotation, meaning the same side of the Moon is always pointing towards the Earth. My intuition is that it wouldn't make any difference (other than the fact that the whole ...
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3 votes
1 answer
63 views

Is the high-low tide difference greater, on average, at new moon, full moon, or neither?

The difference between high tide and low tide peaks when the moon is full and also when the moon is new. At both of these points in the lunar cycle, the tides are known as "spring" tides. On ...
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1 vote
1 answer
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At what rate does the right ascension and declination of a planet, the sun and moon change per hour?

I'm currently building a web app and am getting the RA's and Dec's of solar system objects based on date and time chosen by the user. Then using the gmst for 0 hours of the date, the app calculates ...
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20 votes
2 answers
4k views

Where in space would the Earth and Moon appear to be the same size?

If I'm directly in between the Earth and Moon, what distance from the Earth would I have to be so that the Earth and Moon have the same apparent size? How big would the moon appear compared to it's ...
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15 votes
3 answers
2k views

Was lunar libration first observed or first predicted? In either case, who was the responsible party?

How old is the idea of the far side of the Moon? got me thinking that as soon as we see the moon librate we have to come to terms with there being even more of it we can't see. The Moon's libration is ...
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3 votes
1 answer
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How old is the idea of the far side of the Moon?

The far side of the Moon is the side which always faces away from the Earth, due to tidal locking. Due to libration, about 18% of this far side can be seen at one point or another through telescopes. ...
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1 vote
0 answers
53 views

Which edge of the Moon was deeper submerged into the Earth's shadow?

I was trying to solve this little task: An Australian astronomer at the latitude of Melbourne (-38 °) observed a series of unusual events. First, he watched the setting of the sun and the rising of ...
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21 votes
4 answers
4k views

Where is it possible to observe the Moon for 24 hours?

I wrote an astronomy olympiad yesterday and there was one task I couldn't figure out an answer to: Estimate at what latitudes it is possible to observe the Moon for at least 24 hours. Under what ...
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11 votes
3 answers
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Can you see the shadow of a spaceship on the Moon while looking towards the Earth?

It's a classic movie cliche. We see the surface of the Moon with the Earth in the distance and a dark shadow of an invading alien spaceship slowly covering the landscape. We see this in the opening ...
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4 votes
3 answers
268 views

How to calculate the nodal precession range of the Moon with respect to the celestial equator?

In the span of 18.6 years there is nodal precession of the Moon with respect to the ecliptic of 360 deg. But if we consider this precession with respect to the equator, we will find (unless I'm hugely ...
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2 votes
2 answers
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do meteroid impacts occur evenly across the entire moon surface?

Since the moon is tidally locked and has the same face showing to the earth, I would expect that the earth's shadow represents an area on the moon that would be spared some meteoroid impacts. Does the ...
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2 votes
0 answers
41 views

Up to what distance from the Moon does the Moon's gravity hold its exosphere before it is being cast away by solar wind?

Up to how far from the Moon is the Moon's exosphere gravitationally bound to it? For the Earth's exosphere it is 120,000 mi (190,000 km) or half the Moon's distance from the Earth, beyond that the ...
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0 votes
0 answers
26 views

Where can I find rise, set & phase data for the MEAN moon?

I am trying to design a javascript time-and-tide-clock for a website. The clock starts when the page is loaded with the initial positions of the time hands pointing to the current time of day. The ...
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1 vote
1 answer
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Why Does Moon Evection formula use the mean position instead of the true position?

Reading Wikipedia on the Moon Evection, and was somewhat surprised to find there that the formulas to express the evection are using the Moon's Mean position (mean anomaly) instead of its True ...
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1 vote
0 answers
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Are new Moons (and full Moons) more probable to happen around certain ecliptic longitudes?

The average lunar synodic month is 29.53059 days. Because of these variations in angular rate, the actual time between lunations may vary from about 29.18 to about 29.93 days. The average duration in ...
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2 votes
6 answers
210 views

Am I looking at the moon upside down here in the US?

This may be a very basic question, but I just learned that the moon orbits around the earth counterclockwise. I always thought the earth and the moon shared the rotation and orbit direction. Since the ...
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3 votes
0 answers
118 views

Why does our Moon not have rings?

While our Moon is full of craters, one could consider that these events might have been enough to release amounts of fragmented mass into the Moon's orbit sufficient to establish some sort of ring. ...
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0 votes
1 answer
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Structures on the Far Side of the Moon?

I downloaded an image of the far side of the moon using Google Earth. It is an area to the North West of the Mare Moscoviense (lat 27.3$^{\circ}$ lon 147.9$^{\circ}$) What are the dot-like structures ...
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2 votes
2 answers
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Why does the difference between terrestrial times and universal time, $\Delta T$, have such a strange behaviour?

I was reading about ancient astronomy, and one of the main phenomena described is eclipses. Now, I read this 2016 paper by Stephenson, Morrison and Hohenkerk, in which they determine the values of the ...
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3 votes
2 answers
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When can Moon occult Venus?

I'm trying to solve this task: At what age of the Moon (in days after the new moon) is it possible for the Moon to occult Venus? How I was solving it: Angular velocity of the Moon is 13.2 degrees ...
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2 votes
2 answers
323 views

What percentage of the time can we see the moon during the day?

From sun rise to sun set what percentage of the time is the moon visible? I saw one thing at the top of google saying an average of 6 hours a day but that seems like a weird way to answer it. Would ...
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4 votes
0 answers
214 views

Trying to find the source of these three orbital elements

I'm working through section 65 “Calculating the Moon's position” in Practical Astronomy with your Calculator or Spreadsheet (fourth edition) by Duffett-Smith and Zwart. They begin the calculations ...
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  • 365
16 votes
3 answers
5k views

Can large scientific telescopes observe the Moon without being damaged?

When I look at the full Moon through my 10cm telescope, it is so bright that it hurts. Can large scientific telescopes observe the moon at all? Does that require special protection equipment? Or ...
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