<p>From a given latitude on Earth, is it possible to calculate the number of days in a year when there is a <a href="https://en.wikipedia.org/wiki/Wet_moon" rel="nofollow noreferrer">wet moon</a> , that is when the moon is lit on the bottom?</p>
<p>If, for example, I want to do the calculation for the year 2023, how should I go about this? And can I predict those days as well?</p>

CC BY-SA 4.0
2023-01-14T02:52:41.767Z
This post describes how to calculate it: https://astronomy.stackexchange.com/questions/39152/how-to-calculate-the-moons-illuminated-fraction-tilt
JohnHoltz
CC BY-SA 4.0
2023-01-14T21:41:07.600Z
Meeus covered this topic in one of the "Morsels" books, though I believe he called it a "moon as a boat".  He did not show how to calculate it, but showed the results of where it could happen and how often.
Greg Miller
<the-moon><orbital-mechanics>
From a given latitude on Earth, how to calculate the number of days in a year when the moon is lit on the bottom?
William
# From a given latitude on Earth, how to calculate the number of days in a year when the moon is lit on the bottom?

(Asked by: username_0 on 2023-01-13)

From a given latitude on Earth, is it possible to calculate the number of days in a year when there is a [wet moon](https://en.wikipedia.org/wiki/Wet_moon) , that is when the moon is lit on the bottom?

If, for example, I want to do the calculation for the year 2023, how should I go about this? And can I predict those days as well?

**Tags:** the-moon, orbital-mechanics

> **Comments:**
> **username_1**: This post describes how to calculate it: https://astronomy.stackexchange.com/questions/39152/how-to-calculate-the-moons-illuminated-fraction-tilt  
> **username_2**: Meeus covered this topic in one of the "Morsels" books, though I believe he called it a "moon as a boat".  He did not show how to calculate it, but showed the results of where it could happen and how often.  

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