<p><a href="https://photoephemeris.com/en" rel="nofollow noreferrer">The Photographers Ephemeris</a> is a very nice tool to give you the direction and time of both Moon and Sunset and -rise, made for exactly that purpose: plan and time shots to be at the right place and time for an awesome scenery.</p>
<p>Other programmes and tools to tell you rise and set times are</p>
<ul>
<li><a href="https://stellarium.org/" rel="nofollow noreferrer">Stellarium</a></li>
<li><a href="https://www.heavens-above.com/" rel="nofollow noreferrer">heavens above</a></li>
<li><a href="https://www.timeanddate.de/astronomie/" rel="nofollow noreferrer">time and date</a></li>
</ul>

CC BY-SA 4.0
2021-03-23T18:52:02.207Z
2021-03-23T18:58:04.973Z
2021-03-23T18:58:04.973Z
planetmaker
<p>As noted above, many sites will give you sunrise and sunset times, but both refer to when the entire Sun is below the horizon.</p>
<p>You appear to be looking for when the Sun (or Moon) is touching the horizon, not when it goes completely below the horizon.</p>
<p>The Sun sets when its geometric position is 50 minutes of arc <em>below</em> the horizon (because of refraction and the Sun's angular diameter), so the Sun touches the horizon when its geometric position is 18 minutes of arc below the horizon.</p>
<p>When that happens, the object you want to photograph should have an angular diameter of 16 minutes of arc, just like the Sun.</p>
<p>One caveat: because of refraction, the Sun's diameter isn't exactly 16 minutes of arc when it starts setting, but should be fairly close.</p>

CC BY-SA 4.0
2021-03-28T12:02:15.840Z
are you throwing random numbers around?
jumpjack
CC BY-SA 4.0
2021-03-28T13:39:15.717Z
@jumpjackNo. These are established numbers for refraction at the horizon and the Sun's angular diameter.
Guest
CC BY-SA 4.0
2021-03-28T05:37:59.767Z
2021-03-28T05:37:59.767Z
Guest
<blockquote>
<p>How to determine when Sun/Moon is aligned to two location on Earth's surface?</p>
</blockquote>
<p>First check out the many answers to our canonical <a href="https://astronomy.stackexchange.com/q/13488">Where can I find the positions of the planets, stars, moons, artificial satellites, etc. and visualize them?</a></p>
<hr />
<p>Both Horizons and Skyfield below are based on NASA JPL <a href="https://en.wikipedia.org/wiki/Jet_Propulsion_Laboratory_Development_Ephemeris" rel="nofollow noreferrer">Development Ephemerides</a> and so are rock-solid accurate and reliable.</p>
<h3>NASA JPL Horizons:</h3>
<p><a href="https://ssd.jpl.nasa.gov/horizons.cgi" rel="nofollow noreferrer">Horizons</a> and the Spice infrastructure provide ways to search for specific events. You can read more about spice here in Astronomy <a href="https://astronomy.stackexchange.com/search?q=spice">~40 posts</a> and also in Space Exploration SE <a href="https://space.stackexchange.com/search?q=spice">~100 posts</a>.</p>
<h3>Python</h3>
<p>If you can use Python then Skyfield has several methods for finding events. See the <a href="https://rhodesmill.org/skyfield/api.html#searching" rel="nofollow noreferrer">Searching</a> and <a href="https://rhodesmill.org/skyfield/api.html#almanac" rel="nofollow noreferrer">Almanac</a> headings. This package has been under active development for years and has all kinds of helpful methods and goodies!</p>
<p>Here's an old example of a photographer's sunset question based on a specific location on Earth that I answered using a Skyfield script. I think that today it would be written even more easily using the newer features described above! <a href="https://astronomy.stackexchange.com/q/30098/7982">Sunset on [Mountain] from [Viewing Point]</a></p>
<p><a href="https://i.sstatic.net/PTpEl.png" rel="nofollow noreferrer"><img src="https://i.sstatic.net/PTpElm.png" alt="from https://astronomy.stackexchange.com/q/30098/7982" /></a> <a href="https://i.sstatic.net/r3t8h.png" rel="nofollow noreferrer"><img src="https://i.sstatic.net/r3t8hm.png" alt="from https://astronomy.stackexchange.com/q/30098/7982" /></a></p>
<p>click for larger</p>

CC BY-SA 4.0
2021-03-29T11:39:55.957Z
I like Skyfield graphical representations, but I don't use Python, so I'll steal the idea and will try implementing it in javascript using Astronomy library :-)  https://github.com/cosinekitty/astronomy
jumpjack
CC BY-SA 4.0
2021-03-24T02:35:38.683Z
2021-03-24T05:08:39.630Z
2021-03-24T05:08:39.630Z
uhoh
<p>I would like to make a photo to Moon/Sun when it is very low on horizon, so if I make the shot far away from an object on Earth surface, it appears as big as the Sun.</p>
<p>But how can I calculate the right moment? Any site or app? Could NASA Horizons help? I made a GUI for it, but don't know if any quantity I can query could give me the information  I need:</p>
<p><a href="http://win98.altervista.org/space/exploration/NHUGUI.html" rel="nofollow noreferrer">http://win98.altervista.org/space/exploration/NHUGUI.html</a></p>

CC BY-SA 4.0
2021-03-24T02:23:49.653Z
If you can use Python then Skyfield several methods for finding events. See the [Searching](https://rhodesmill.org/skyfield/api.html#searching) and [Almanac](https://rhodesmill.org/skyfield/api.html#almanac) headings.
uhoh
<the-sun><the-moon><photography><ephemeris>
How to determine when Sun/Moon is aligned to two location on Earth's surface?
jumpjack
# How to determine when Sun/Moon is aligned to two location on Earth's surface?

(Asked by: username_0 on 2021-03-23)

I would like to make a photo to Moon/Sun when it is very low on horizon, so if I make the shot far away from an object on Earth surface, it appears as big as the Sun.

But how can I calculate the right moment? Any site or app? Could NASA Horizons help? I made a GUI for it, but don't know if any quantity I can query could give me the information I need:

<http://win98.altervista.org/space/exploration/NHUGUI.html>

**Tags:** the-sun, the-moon, photography, ephemeris
> **Comments:**
> **username_1**: If you can use Python then Skyfield several methods for finding events. See the [Searching](https://rhodesmill.org/skyfield/api.html#searching) and [Almanac](https://rhodesmill.org/skyfield/api.html#almanac) headings.  

---

## 3 answers

### Answer by username_2 on 2021-03-23. Score: 4 | Accepted answer

[The Photographers Ephemeris](https://photoephemeris.com/en) is a very nice tool to give you the direction and time of both Moon and Sunset and -rise, made for exactly that purpose: plan and time shots to be at the right place and time for an awesome scenery.

Other programmes and tools to tell you rise and set times are

* [Stellarium](https://stellarium.org/)
* [heavens above](https://www.heavens-above.com/)
* [time and date](https://www.timeanddate.de/astronomie/)


---

### Answer by username_3 on 2021-03-28. Score: 1

As noted above, many sites will give you sunrise and sunset times, but both refer to when the entire Sun is below the horizon.

You appear to be looking for when the Sun (or Moon) is touching the horizon, not when it goes completely below the horizon.

The Sun sets when its geometric position is 50 minutes of arc *below* the horizon (because of refraction and the Sun's angular diameter), so the Sun touches the horizon when its geometric position is 18 minutes of arc below the horizon.

When that happens, the object you want to photograph should have an angular diameter of 16 minutes of arc, just like the Sun.

One caveat: because of refraction, the Sun's diameter isn't exactly 16 minutes of arc when it starts setting, but should be fairly close.

> **Comments:**
> **username_0**: are you throwing random numbers around?  
> **username_3**: @jumpjackNo. These are established numbers for refraction at the horizon and the Sun's angular diameter.  

---

### Answer by username_1 on 2021-03-24. Score: 0

> How to determine when Sun/Moon is aligned to two location on Earth's surface?

First check out the many answers to our canonical [Where can I find the positions of the planets, stars, moons, artificial satellites, etc. and visualize them?](https://astronomy.stackexchange.com/q/13488)

---

Both Horizons and Skyfield below are based on NASA JPL [Development Ephemerides](https://en.wikipedia.org/wiki/Jet_Propulsion_Laboratory_Development_Ephemeris) and so are rock-solid accurate and reliable.

### NASA JPL Horizons:

[Horizons](https://ssd.jpl.nasa.gov/horizons.cgi) and the Spice infrastructure provide ways to search for specific events. You can read more about spice here in Astronomy [~40 posts](https://astronomy.stackexchange.com/search?q=spice) and also in Space Exploration SE [~100 posts](https://space.stackexchange.com/search?q=spice).

### Python

If you can use Python then Skyfield has several methods for finding events. See the [Searching](https://rhodesmill.org/skyfield/api.html#searching) and [Almanac](https://rhodesmill.org/skyfield/api.html#almanac) headings. This package has been under active development for years and has all kinds of helpful methods and goodies!

Here's an old example of a photographer's sunset question based on a specific location on Earth that I answered using a Skyfield script. I think that today it would be written even more easily using the newer features described above! [Sunset on [Mountain] from [Viewing Point]](https://astronomy.stackexchange.com/q/30098/7982)

[![from https://astronomy.stackexchange.com/q/30098/7982](https://i.sstatic.net/PTpElm.png)](https://i.sstatic.net/PTpEl.png) [![from https://astronomy.stackexchange.com/q/30098/7982](https://i.sstatic.net/r3t8hm.png)](https://i.sstatic.net/r3t8h.png)

click for larger

> **Comments:**
> **username_0**: I like Skyfield graphical representations, but I don't use Python, so I'll steal the idea and will try implementing it in javascript using Astronomy library :-)  https://github.com/cosinekitty/astronomy  

---

