<p><strong>tl;dr:</strong> To an accuracy of about a half of a day:</p>
<ul>
<li><strong>Third quarter is sunrise</strong> for Chang'e-4 and Yutu-2</li>
<li><strong>First quarter is sunset</strong> for Chang'e-4 and Yutu-2</li>
</ul>
<hr />
<h2>Moon seen from Earth:</h2>
<p>From Wikipedia's article <a href="https://en.wikipedia.org/wiki/Selenographic_coordinates" rel="nofollow noreferrer">Selenographic coordinates</a></p>
<blockquote>
<p>Longitude</p>
<p>Longitude on the Moon is measured both east and west from its prime meridian. When no direction is specified, east is positive and west is negative.</p>
<p>Roughly speaking, the Moon's prime meridian lies near the center of the Moon's disc as seen from Earth. For precise applications, many coordinate systems have been defined for the Moon, each with a slightly different prime meridian. The IAU recommends the &quot;mean Earth/polar axis&quot; system,<sup>2</sup> in which the prime meridian is the average direction (from the Moon's center) of the Earth's center.<sup>3</sup></p>
<p><sup>2</sup> <a href="https://astrogeology.usgs.gov/Projects/WGCCRE/WGCCRE2003preprint.pdf" rel="nofollow noreferrer">https://astrogeology.usgs.gov/Projects/WGCCRE/WGCCRE2003preprint.pdf</a></p>
<p><sup>3</sup> <a href="http://lunar.gsfc.nasa.gov/library/451-SCI-000958.pdf" rel="nofollow noreferrer">http://lunar.gsfc.nasa.gov/library/451-SCI-000958.pdf</a></p>
</blockquote>
<hr />
<p>Simplifying further, <em>seen from Earth</em>, <strong>0° longitude <a href="https://en.wikipedia.org/wiki/Libration" rel="nofollow noreferrer">wobbles</a> near the center of the lunar disk.</strong> (see also <a href="https://space.stackexchange.com/q/19936/12102">1</a>, <a href="https://physics.stackexchange.com/q/251700/83380">2</a>, <a href="https://space.stackexchange.com/q/14943/12102">3</a>)</p>
<h2>Chang'e-4:</h2>
<p><a href="https://en.wikipedia.org/wiki/Chang%27e_4" rel="nofollow noreferrer">Chang'e-4</a> is in <a href="https://en.wikipedia.org/wiki/Von_K%C3%A1rm%C3%A1n_(lunar_crater)" rel="nofollow noreferrer">Von Kármán crater</a> (also <a href="https://tools.wmflabs.org/geohack/geohack.php?pagename=Von_K%C3%A1rm%C3%A1n_(lunar_crater)&amp;params=44.8_S_175.9_E_globe:moon_type:landmark" rel="nofollow noreferrer">here</a>) at about 44.8° South, <strong>175.9° East.</strong></p>
<p>So <strong>Chang'e-4 and Yutu-2 sit almost diametrically opposed to the Earth</strong> longitude-wise, and so sunset on the Moon's prime meridian is close to sunrise for the pair, and vice-verse.</p>
<h2>Answer:</h2>
<blockquote>
<p>What phases of the Moon as seen from Earth correspond to times of sunrise and sunset for those two?</p>
</blockquote>
<ul>
<li>First quarter is sunset for Chang'e-4 and Yutu-2</li>
<li>Third quarter is sunrise for Chang'e-4 and Yutu-2</li>
</ul>
<hr />
<h2>Location Confirmation:</h2>
<p>We know where Chang'e-4 landed because it returned video of it's own landing.</p>
<p><strong>YouTube Video:</strong> <a href="https://www.youtube.com/watch?v=jyjyf4ANGIo" rel="nofollow noreferrer">https://www.youtube.com/watch?v=jyjyf4ANGIo</a></p>
<p>From <a href="https://space.stackexchange.com/q/33495/12102">How did Chang'e-4 hover, rotate, and then descend so gracefully? (Video)</a>.</p>
<p>Additional verification that Chang'e-4 and Yutu-2 are in Von Kármán crater:</p>
<p>From <a href="http://lroc.sese.asu.edu/about" rel="nofollow noreferrer">The Lunar Reconnaissance Orbiter Camera</a> recent post <a href="http://lroc.sese.asu.edu/posts/1090" rel="nofollow noreferrer">First Look: Chang'e 4</a>:</p>
<p><a href="https://i.sstatic.net/RmU9H.png" rel="nofollow noreferrer"><img src="https://i.sstatic.net/RmU9H.png" alt="enter image description here" /></a></p>
<blockquote>
<p>Arrows indicate position of Chang'e 4 lander on the floor of Von Kármán crater. The sharp crater behind and to the left of the landing site is 3900 meters across (12,800 feet) and 600 meters (1970 feet) deep. Image was shrunk by more than a factor of ten (full resolution available inside the post). LROC NAC M1303521387LR [NASA/GSFC/Arizona State University].</p>
</blockquote>
<p><a href="https://i.sstatic.net/hZRiS.png" rel="nofollow noreferrer"><img src="https://i.sstatic.net/hZRiS.png" alt="enter image description here" /></a></p>
<blockquote>
<p>Area around lander enlarged by a factor of two relative to the native pixel scale (see zoomify below), bright speck between two arrows is the lander. The large crater in the center (just right and below arrows) is about 440 meters (1440 feet) across. LROC NAC M1303521387LR [NASA/GSFC/Arizona State University].</p>
</blockquote>

CC BY-SA 4.0
2019-02-07T00:37:10.790Z
2019-02-07T01:04:58.203Z
2020-06-17T09:47:40.653Z
uhoh
<p>Firecrackers all night and all libraries being closed here are two good indicators to a nerd like me that <a href="https://en.wikipedia.org/wiki/Lunar_New_Year" rel="nofollow noreferrer">Lunar New Year</a> has come again, and that means that it's the beginning of a lunar month and new Moon as seen from Earth.</p>

<p>That also means that the Chinese lander <a href="https://en.wikipedia.org/wiki/Chang%27e_4" rel="nofollow noreferrer">Chang'e-4</a> and rover <a href="https://en.wikipedia.org/wiki/Chang%27e_4#Chang&#39;e_lander_and_Yutu-2_rover" rel="nofollow noreferrer">Yutu-2</a> should be in sunlight since they are on the far side of the Moon. </p>

<p>What phases of the Moon <em>as seen from Earth</em> correspond to times of sunrise and sunset for those two?</p>

<the-moon>
Happy lunar new year! When will "sunset" happen for Chang'e-4 and Yutu-2?
uhoh
# Happy lunar new year! When will "sunset" happen for Chang'e-4 and Yutu-2?

(Asked by: username_0 on 2019-02-06)

Firecrackers all night and all libraries being closed here are two good indicators to a nerd like me that [Lunar New Year](https://en.wikipedia.org/wiki/Lunar_New_Year) has come again, and that means that it's the beginning of a lunar month and new Moon as seen from Earth.

That also means that the Chinese lander [Chang'e-4](https://en.wikipedia.org/wiki/Chang%27e_4) and rover [Yutu-2](https://en.wikipedia.org/wiki/Chang%27e_4#Chang'e_lander_and_Yutu-2_rover) should be in sunlight since they are on the far side of the Moon.

What phases of the Moon *as seen from Earth* correspond to times of sunrise and sunset for those two?

**Tags:** the-moon


---

## 1 answers

### Answer by username_0 on 2019-02-07. Score: 2 | Accepted answer

**tl;dr:** To an accuracy of about a half of a day:

* **Third quarter is sunrise** for Chang'e-4 and Yutu-2
* **First quarter is sunset** for Chang'e-4 and Yutu-2

---

## Moon seen from Earth:

From Wikipedia's article [Selenographic coordinates](https://en.wikipedia.org/wiki/Selenographic_coordinates)

> Longitude
>
> Longitude on the Moon is measured both east and west from its prime meridian. When no direction is specified, east is positive and west is negative.
>
> Roughly speaking, the Moon's prime meridian lies near the center of the Moon's disc as seen from Earth. For precise applications, many coordinate systems have been defined for the Moon, each with a slightly different prime meridian. The IAU recommends the "mean Earth/polar axis" system,2 in which the prime meridian is the average direction (from the Moon's center) of the Earth's center.3
>
> 2 <https://astrogeology.usgs.gov/Projects/WGCCRE/WGCCRE2003preprint.pdf>
>
> 3 <http://lunar.gsfc.nasa.gov/library/451-SCI-000958.pdf>

---

Simplifying further, *seen from Earth*, **0° longitude [wobbles](https://en.wikipedia.org/wiki/Libration) near the center of the lunar disk.** (see also [1](https://space.stackexchange.com/q/19936/12102), [2](https://physics.stackexchange.com/q/251700/83380), [3](https://space.stackexchange.com/q/14943/12102))

## Chang'e-4:

[Chang'e-4](https://en.wikipedia.org/wiki/Chang%27e_4) is in [Von Kármán crater](https://en.wikipedia.org/wiki/Von_K%C3%A1rm%C3%A1n_(lunar_crater)) (also [here](https://tools.wmflabs.org/geohack/geohack.php?pagename=Von_K%C3%A1rm%C3%A1n_(lunar_crater)¶ms=44.8_S_175.9_E_globe:moon_type:landmark)) at about 44.8° South, **175.9° East.**

So **Chang'e-4 and Yutu-2 sit almost diametrically opposed to the Earth** longitude-wise, and so sunset on the Moon's prime meridian is close to sunrise for the pair, and vice-verse.

## Answer:

> What phases of the Moon as seen from Earth correspond to times of sunrise and sunset for those two?

* First quarter is sunset for Chang'e-4 and Yutu-2
* Third quarter is sunrise for Chang'e-4 and Yutu-2

---

## Location Confirmation:

We know where Chang'e-4 landed because it returned video of it's own landing.

**YouTube Video:** <https://www.youtube.com/watch?v=jyjyf4ANGIo>

From [How did Chang'e-4 hover, rotate, and then descend so gracefully? (Video)](https://space.stackexchange.com/q/33495/12102).

Additional verification that Chang'e-4 and Yutu-2 are in Von Kármán crater:

From [The Lunar Reconnaissance Orbiter Camera](http://lroc.sese.asu.edu/about) recent post [First Look: Chang'e 4](http://lroc.sese.asu.edu/posts/1090):

[![enter image description here](https://i.sstatic.net/RmU9H.png)](https://i.sstatic.net/RmU9H.png)

> Arrows indicate position of Chang'e 4 lander on the floor of Von Kármán crater. The sharp crater behind and to the left of the landing site is 3900 meters across (12,800 feet) and 600 meters (1970 feet) deep. Image was shrunk by more than a factor of ten (full resolution available inside the post). LROC NAC M1303521387LR [NASA/GSFC/Arizona State University].

[![enter image description here](https://i.sstatic.net/hZRiS.png)](https://i.sstatic.net/hZRiS.png)

> Area around lander enlarged by a factor of two relative to the native pixel scale (see zoomify below), bright speck between two arrows is the lander. The large crater in the center (just right and below arrows) is about 440 meters (1440 feet) across. LROC NAC M1303521387LR [NASA/GSFC/Arizona State University].


---

