# Tag Info

### The exact definition of lunar eclipse

The exact definition of X can be a challenge, because any definition can be by itself "exact" even if wrong or disputed, and the premise of using the word "The" is that there can ...
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1 vote

### Can the Celestron Powerseeker 127EQ observe the moon during day time?

There should be absolutely no problem at all seeing the bright, sun-illuminated part of the Moon during the day at 1000 mm / 20 mm = 50x through your telescope. The part that's not illuminated by the ...
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### Is there a Lagrange point between the earth and the moon?

Yes, the Earth-Moon system has Lagrange points, and Wikipedia has a short list of satellites that have (or will) orbited near L2, L4 or L5. Neither L1 nor L3 appear to be popular. The Moon's orbit ...
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### What is the **actual** average distance of the Moon from Earth?

Lunar theory is complicated. ;) The Moon's orbit around the Earth is only approximately a constant Keplerian ellipse. As I mentioned here, the Moon's orbit around the Earth-Moon barycentre has an ...
• 8,947

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

Your guess on the requirement for calculus is correct. What you need to do is integrate the moon's distance over one orbit to find an average distance. Starting from the equation below, the Moon's (or ...
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### Is there a Lagrange point between the earth and the moon?

@JamesK's answer is good, but I'll address some of your points more specifically. Is there a Lagrange point between the Earth and Moon... Yes, it is called Earth-Moon L1 (to distinguish it from Sun-...
• 31.4k
Accepted

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

Mean distance averaged over time for any Keplerian orbit is $a(1+\frac{1}{2}e^2)$, where $a$ is the semi-major axis and $e$ is the eccentricity. Using your NASA fact sheet, I get about 384,979 km for ...
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