<p>Not quite.</p>
<p>The angle of the Moon's orbital plane with respect to the ecliptic is fairly constant at ~5.1° with a bit of variation as pointed out by @PM2Ring in their comment. The orbit and the plane defined by it does not change (much).</p>
<p>Over the duration of one month the Moon moves along its orbit. Thus its <em>position</em> changes during these days from a position about 5.1 degrees below the ecliptic to on on the ecliptic 7 days later to one 5.1 degrees above 14 days later - and back to -5.1° when the orbit is completed one month later.</p>
<p>Thus:</p>
<p>The Moon's <em>orbital path</em> around Earth is tilted <em>by</em> 5.1 degrees.</p>
<p>The Moon's <em>position</em> varies <em>up to</em> 5.1 degrees below and above the ecliptic.</p>

CC BY-SA 4.0
2024-03-28T06:53:00.993Z
2024-03-28T06:53:00.993Z
planetmaker
<blockquote>
<p>Is this a correct understanding?</p>
</blockquote>
<p>Not exactly. The Sun is a huge perturber of the Moon's orbit. From a heliocentric perspective, the gravitational acceleration of the Moon toward the Sun is over twice that of the Moon toward the Earth. From a geocentric perspective, the Sun is still a huge huge perturber of the Moon's orbit about the Earth. It wasn't until the early 20th century that a fairly accurate description of the Moon's orbit was developed, primarily due to this huge perturbation. The other planets and the Earth's not-quite spherical shape also perturb the Moon's orbit, but to a much lesser extent than the Sun.</p>
<p>That said, the inclination of the Moon's orbit with respect to the ecliptic is fairly constant. Below is a plot of the Moon's instantaneous (osculating) inclination:</p>
<p><a href="https://i.sstatic.net/XTg2q.png" rel="nofollow noreferrer"><img src="https://i.sstatic.net/XTg2q.png" alt="Lunar orbit inclination for 2008 to 2010" /></a><br />
<sub>Source: <a href="https://eclipse.gsfc.nasa.gov/SEhelp/moonorbit.html" rel="nofollow noreferrer">Eclipses and the Moon's orbit</a> at nasa.gov</sub></p>
<p>Note that the inclination varies from less than 5.0° to about 5.3°, with a mean of 5.145°. So, not quite constant, but still, fairly constant.</p>

CC BY-SA 4.0
2024-03-29T03:26:31.640Z
2024-03-29T03:26:31.640Z
David Hammen
<p>I've come across a number of sources (<a href="https://www.space.com/how-total-solar-eclipse-2024-will-differ-from-2017-solar-eclips" rel="nofollow noreferrer">example</a>) saying some variation of this:</p>
<blockquote>
<p>The moon's orbital path around Earth is tilted by 5.1 degrees with respect to the orbit of the Earth around the sun.</p>
</blockquote>
<p>This isn't strictly true though, right? Per <a href="https://en.wikipedia.org/wiki/Lunar_standstill" rel="nofollow noreferrer">this article</a>, the angle of the moon's orbit varies by something like +/-5 degrees. So really we should say &quot;The moon's orbital path around Earth is tilted by <em><strong>up to</strong></em> 5.1 degrees&quot;.</p>
<p>Is this a correct understanding?</p>

CC BY-SA 4.0
2024-03-28T01:12:50.500Z
I think you're misreading the lunar standstill article. It's just saying that the Moon's ~5.1° inclination to the ecliptic (which is inclined by ~23.5° to the equator) means that the Moon's maximum declination range varies over the nodal precession cycle from ±(23.5°-5.1°) to ±(23.5+5.1°). I have some info on the lunar declination & standstill here: https://astronomy.stackexchange.com/a/50974/16685 That answer is in response to a kind of complicated question, so some of the info & graphs may be a little confusing. ;)
PM 2Ring
CC BY-SA 4.0
2024-03-28T01:16:57.157Z
The Moon's inclination to the ecliptic varies from ~5° to ~5.3° in a rather complicated way. I have graphs of the inclination and other lunar orbital elements here: https://astronomy.stackexchange.com/a/55112/16685
PM 2Ring
<the-moon><orbit><precession>
Is the Moon's orbital plane angle relative to the ecliptic constant?
Stephen W.
# Is the Moon's orbital plane angle relative to the ecliptic constant?

(Asked by: username_0 on 2024-03-28)

I've come across a number of sources ([example](https://www.space.com/how-total-solar-eclipse-2024-will-differ-from-2017-solar-eclips)) saying some variation of this:

> The moon's orbital path around Earth is tilted by 5.1 degrees with respect to the orbit of the Earth around the sun.

This isn't strictly true though, right? Per [this article](https://en.wikipedia.org/wiki/Lunar_standstill), the angle of the moon's orbit varies by something like +/-5 degrees. So really we should say "The moon's orbital path around Earth is tilted by ***up to*** 5.1 degrees".

Is this a correct understanding?

**Tags:** the-moon, orbit, precession
> **Comments:**
> **username_1**: I think you're misreading the lunar standstill article. It's just saying that the Moon's ~5.1° inclination to the ecliptic (which is inclined by ~23.5° to the equator) means that the Moon's maximum declination range varies over the nodal precession cycle from ±(23.5°-5.1°) to ±(23.5+5.1°). I have some info on the lunar declination & standstill here: https://astronomy.stackexchange.com/a/50974/16685 That answer is in response to a kind of complicated question, so some of the info & graphs may be a little confusing. ;)  
> **username_1**: The Moon's inclination to the ecliptic varies from ~5° to ~5.3° in a rather complicated way. I have graphs of the inclination and other lunar orbital elements here: https://astronomy.stackexchange.com/a/55112/16685  

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## 2 answers

### Answer by username_2 on 2024-03-28. Score: 2 | Accepted answer

Not quite.

The angle of the Moon's orbital plane with respect to the ecliptic is fairly constant at ~5.1° with a bit of variation as pointed out by @PM2Ring in their comment. The orbit and the plane defined by it does not change (much).

Over the duration of one month the Moon moves along its orbit. Thus its *position* changes during these days from a position about 5.1 degrees below the ecliptic to on on the ecliptic 7 days later to one 5.1 degrees above 14 days later - and back to -5.1° when the orbit is completed one month later.

Thus:

The Moon's *orbital path* around Earth is tilted *by* 5.1 degrees.

The Moon's *position* varies *up to* 5.1 degrees below and above the ecliptic.


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### Answer by username_3 on 2024-03-29. Score: 1

> Is this a correct understanding?

Not exactly. The Sun is a huge perturber of the Moon's orbit. From a heliocentric perspective, the gravitational acceleration of the Moon toward the Sun is over twice that of the Moon toward the Earth. From a geocentric perspective, the Sun is still a huge huge perturber of the Moon's orbit about the Earth. It wasn't until the early 20th century that a fairly accurate description of the Moon's orbit was developed, primarily due to this huge perturbation. The other planets and the Earth's not-quite spherical shape also perturb the Moon's orbit, but to a much lesser extent than the Sun.

That said, the inclination of the Moon's orbit with respect to the ecliptic is fairly constant. Below is a plot of the Moon's instantaneous (osculating) inclination:

[![Lunar orbit inclination for 2008 to 2010](https://i.sstatic.net/XTg2q.png)](https://i.sstatic.net/XTg2q.png)  
Source: [Eclipses and the Moon's orbit](https://eclipse.gsfc.nasa.gov/SEhelp/moonorbit.html) at nasa.gov

Note that the inclination varies from less than 5.0° to about 5.3°, with a mean of 5.145°. So, not quite constant, but still, fairly constant.


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