<p>At the accuracy you need, the calculation can be quite simple:  It takes 12 hours and 26 minutes for the moon to go from "overhead" to "underfoot", and 12 hours 26 minutes to go from "underfoot to overhead".</p>

<p>So if you notice that the moon is overhead at 20:00 one evening, it will be overhead at 20:52 the next evening,  then 21:44, 22:36 and so on.  (Or, even easier,  approximate to "50 min" and use "add an hour, minus 10 min"</p>

<p>The actual motion of the moon is rather complicated, as the moon's orbit is elliptical and perturbed by the sun. If you need more accurate values you need to use a complex method of calculation, which is what the websites are using.</p>

<p>If you only have rise and setting time, the culmination will be roughly in the middle</p>

<p>The Solunar calculator page contains some obvious errors (such as on 5th May) </p>

CC BY-SA 4.0
2020-05-11T23:51:00.370Z
Thanks for your answer ! This calculation will suffice for the moment. However, could you add a link for the theory behind the complex method of calculation that you are talking about? (in case I need that in near futur)
Amine Z.
CC BY-SA 4.0
2020-05-12T05:02:11.163Z
Look at the http://astropy.org/ package which has a full implementation. and see the http://www.geoastro.de/TransitCulm/index.html for a description of some of the algorithms involved.
James K
CC BY-SA 4.0
2020-05-11T12:24:07.977Z
2020-05-11T12:24:07.977Z
James K
<p>For hunting purposes, some hunters follow the moon phases to hunt accordingly. To give some context, here's some links:</p>

<ul>
<li>Lunar cycle's effects on hunting: <a href="https://www.acurite.com/blog/weather-stations-with-moon-phase-for-hunting-fishing" rel="nofollow noreferrer">https://www.acurite.com/blog/weather-stations-with-moon-phase-for-hunting-fishing</a></li>
<li>Solunar theory: <a href="https://en.wikipedia.org/wiki/Solunar_theory" rel="nofollow noreferrer">https://en.wikipedia.org/wiki/Solunar_theory</a></li>
</ul>

<p>I would like to know how to calculate the time when the moon is directly overhead in the sky (<strong>moon overhead</strong>) and when the moon is directly underfoot in the opposite side of the earth's sky (<strong>moon underfoot</strong>). Those are the information that I have:</p>

<ul>
<li>Moon rise time</li>
<li>Moon set time</li>
<li>Moon phase (first, full, last, new)</li>
</ul>

<p>Those information come from AccuWeather API: <a href="https://apidev.accuweather.com/developers/astronomyAPIGuide#MoonPhasesRange" rel="nofollow noreferrer">https://apidev.accuweather.com/developers/astronomyAPIGuide#MoonPhasesRange</a>. There are some other APIs that give the moon phase in degree format or between 0 and 1 but we chose AccuWeather. </p>

<p>I tried to calculate this with only the moon rise and set time. I thought that simply calculating halfway between rise and set time will suffice. However, I didn't always get the same results as the moon overhead and underfoot in this website: <a href="http://www.solunarforecast.com/solunarcalendar.aspx" rel="nofollow noreferrer">http://www.solunarforecast.com/solunarcalendar.aspx</a></p>

<p>Is there a formula to get the time of moon overhead and underfoot with the information that I have?</p>

<p><strong>UPDATE</strong></p>

<p>I used the definition</p>

<blockquote>
  <p>when the moon is directly overhead in the sky</p>
</blockquote>

<p>because that is what I found from my research. However, it's seems the correct definition is <strong>when the moon is at highest point in the sky</strong>.</p>

<p>Also, since it's for hunting purposes, I don't need the time to be accurate to the minute (but that could be nice).</p>

CC BY-SA 4.0
2020-05-11T05:35:56.870Z
The term "directly" is problematic. Do you mean within 1 degree, or 1 arc second, or *exactly?* Of course *exactly* won't get you any useful results. Just for example see answers to [How long does it take for ISS to travel over all possible places of the world one time?](https://space.stackexchange.com/q/19553/12102) and [What are the chances that the ISS transits the moon as seen from your house (or headquarters)?](https://space.stackexchange.com/q/29879/12102)
uhoh
CC BY-SA 4.0
2020-05-11T06:54:05.907Z
It appears from the link that you gave that you are not talking about the moon being literally overhead,  but being at it's highest point.  This is called the culmination of the moon. It also depends on how accurate you need the answer to be, and that in turn depends on why you need this.  It also depends on what you mean by "simple".  Is trigonometry "simple"? Is http://www.geoastro.de/TransitCulm/index.html simple?
James K
CC BY-SA 4.0
2020-05-11T12:04:46.827Z
@JamesK I've updated my question to give more context. Also, you're right it's when the moon is the highest point in the sky for moon overhead. Thanks for pointing out !
Amine Z.
<the-moon><moon-phases>
How to calculate moon overhead and underfoot time?
Amine Z.
# How to calculate moon overhead and underfoot time?

(Asked by: username_0 on 2020-05-11)

For hunting purposes, some hunters follow the moon phases to hunt accordingly. To give some context, here's some links:

* Lunar cycle's effects on hunting: <https://www.acurite.com/blog/weather-stations-with-moon-phase-for-hunting-fishing>
* Solunar theory: <https://en.wikipedia.org/wiki/Solunar_theory>

I would like to know how to calculate the time when the moon is directly overhead in the sky (**moon overhead**) and when the moon is directly underfoot in the opposite side of the earth's sky (**moon underfoot**). Those are the information that I have:

* Moon rise time
* Moon set time
* Moon phase (first, full, last, new)

Those information come from AccuWeather API: <https://apidev.accuweather.com/developers/astronomyAPIGuide#MoonPhasesRange>. There are some other APIs that give the moon phase in degree format or between 0 and 1 but we chose AccuWeather.

I tried to calculate this with only the moon rise and set time. I thought that simply calculating halfway between rise and set time will suffice. However, I didn't always get the same results as the moon overhead and underfoot in this website: <http://www.solunarforecast.com/solunarcalendar.aspx>

Is there a formula to get the time of moon overhead and underfoot with the information that I have?

**UPDATE**

I used the definition

> when the moon is directly overhead in the sky

because that is what I found from my research. However, it's seems the correct definition is **when the moon is at highest point in the sky**.

Also, since it's for hunting purposes, I don't need the time to be accurate to the minute (but that could be nice).

**Tags:** the-moon, moon-phases

> **Comments:**
> **username_1**: The term "directly" is problematic. Do you mean within 1 degree, or 1 arc second, or *exactly?* Of course *exactly* won't get you any useful results. Just for example see answers to [How long does it take for ISS to travel over all possible places of the world one time?](https://space.stackexchange.com/q/19553/12102) and [What are the chances that the ISS transits the moon as seen from your house (or headquarters)?](https://space.stackexchange.com/q/29879/12102)  
> **username_2**: It appears from the link that you gave that you are not talking about the moon being literally overhead,  but being at it's highest point.  This is called the culmination of the moon. It also depends on how accurate you need the answer to be, and that in turn depends on why you need this.  It also depends on what you mean by "simple".  Is trigonometry "simple"? Is http://www.geoastro.de/TransitCulm/index.html simple?  
> **username_0**: @JamesK I've updated my question to give more context. Also, you're right it's when the moon is the highest point in the sky for moon overhead. Thanks for pointing out !  

---

## 1 answers

### Answer by username_2 on 2020-05-11. Score: 2 | Accepted answer

At the accuracy you need, the calculation can be quite simple: It takes 12 hours and 26 minutes for the moon to go from "overhead" to "underfoot", and 12 hours 26 minutes to go from "underfoot to overhead".

So if you notice that the moon is overhead at 20:00 one evening, it will be overhead at 20:52 the next evening, then 21:44, 22:36 and so on. (Or, even easier, approximate to "50 min" and use "add an hour, minus 10 min"

The actual motion of the moon is rather complicated, as the moon's orbit is elliptical and perturbed by the sun. If you need more accurate values you need to use a complex method of calculation, which is what the websites are using.

If you only have rise and setting time, the culmination will be roughly in the middle

The Solunar calculator page contains some obvious errors (such as on 5th May)

> **Comments:**
> **username_0**: Thanks for your answer ! This calculation will suffice for the moment. However, could you add a link for the theory behind the complex method of calculation that you are talking about? (in case I need that in near futur)  
> **username_2**: Look at the http://astropy.org/ package which has a full implementation. and see the http://www.geoastro.de/TransitCulm/index.html for a description of some of the algorithms involved.  

---

