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I recently found out that the moon's appearance changes based on one's latitude, and while googling for more information I found conflicting images about what the moon's phases look like from the equator.

Some images (Example 1, Example 2) show the light of the moon starts from the bottom and grows up to the top while waxing, and then the shadow falls back down to the bottom while waning. (It's as if the light of the moon is an eyeball and the shadow is an eye lid).

There are other images though (Example 1, Example 2 ), that show the light of the moon starting from the top and "falling" down to the bottom draping the whole moon in light while waxing, and then the shadow starts from the top, then "falls" back down to the bottom draping the moon in shadow while waning.

I am not an knowledgeable on anything relating to astronomy, so I'd like to know: which one is correct?

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    $\begingroup$ The second set of examples you give is wrong. windy.app obviously got things wrong, while the creator of the Shutterstock drawing doesn’t specify it’s on the equator and seems to have created just generic icons. $\endgroup$ Jun 18, 2023 at 19:45
  • $\begingroup$ They are both correct. The view of the Moon will rotate about 180deg from rise to set. The first set of examples show how the Moon will appear at Moonset, the second set shows what it looks like at Moonrise. $\endgroup$ Jun 19, 2023 at 5:12

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Just to pick one aspect, "waxing crescent".

The lit part of the moon will face (along a great circle) towards the sun.

So in the evening, when the sun has set, the waxing crescent will look like

\___/

With the lit part of the moon pointing towards the sun

Of course in the morning, after the sun and moon have risen, and with the sun above the moon in the sky. The moon will look like

 ___
/   \

But the moon will be difficult to see at this time as the sun will be above the horizon, and quite bright.

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  • $\begingroup$ Yes, a waxing crescent pointing down is looking to the east at sunset and pointing up is looking west after sunrise. $\endgroup$ Jun 20, 2023 at 16:47
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The lit portion of the moon always appears to "point" to the sun. When the moon is a crescent, it is frequently not bright enough to be seen unless the sun is below the horizon, but its apparent position relative to the sun is also very close, so a waxing crescent shortly after the new moon is only visible just after sunset, near the horizon in the west, where it sets very shortly thereafter. Conversely, a waning crescent in the days before a new moon rises in the east just before sunrise and is soon impossible to see because the sunlight overwhelms it.

In both cases, the crescent will appear as a U for an observer on the equator. Because the convex edge of a crescent moon always points toward the sun, and because the moon is easiest to see when the sun is below the horizon, crescent moons are most frequently seen with their convex edge closest to the horizon. However, wider crescents, closer to half full, are visible in broad daylight, so you may see a nearly half-full moon rising in the east shortly before solar noon (or setting in the west shortly after) with its concave edge pointing down.

If you could somehow see the 1-day-old crescent moon as if the sun were not there, you would see it rise shortly after the sun with the illuminated portion at the top of the disk. It would then follow the sun through the sky directly overhead (at the equinox, at least) with the illuminated portion of the disk always closest to the sun, and it would set shortly after the sun with the illuminated portion of the disk at the bottom.

If this seems counterintuitive, remember that it isn't the moon that has turned around but you. When you observe the sunrise or moonrise, you're facing to the east, and when you observe the sunset or moonset, you're facing to the west.

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