# How to calculate GEO (geostationary) satellite eclipse time?

The positions of satellites in geostationary orbits can be characterized by their longitude, the longitude of a point on Earth's equator that is nadir to the spacecraft.

Satellites in GEO will sometimes enter the Earth's shadow and experience solar eclipse. Since the Earth's equator is inclined so far from the ecliptic, this eclipsing depends on the time of year as well.

Are there some simple equations that can estimate the star and end times of solar eclipse for a satellite in GEO, based on the satellite's longitude and the time of year?

Alternatively, are there resources available that can be used to make more accurate predictions?

• @uhoh Thank you for attention. Actually the number of formulas does not matter to me. As a result I want to solve the problem. Commented Jul 26, 2018 at 10:25
• e-books, c #, Jscript, or python. But I need to find the way to calculate. I can probably solve it by formula. @uhoh Commented Jul 26, 2018 at 10:37
• @uhoh I write question on Astronomy SE. I hope someone will reply. Commented Jul 26, 2018 at 11:12
• I've been thinking so much about the upcoming lunar eclipse that I completely missed the point that this is about the eclipse of an artificial satellite. It doesn't belong in Astronomy, it does belong here. However, I think the question will still be closed here and still needs some improvement.
– uhoh
Commented Jul 26, 2018 at 11:26
• I've edited the question to make it a bit more suitable for the site. Hopefully this pretty close to what you would like to ask.
– uhoh
Commented Jul 26, 2018 at 11:36

## 1 Answer

There are several web-base calculators available. This one seems to work well; there's more explanation here.

(Generaly, SE answers aren't supposed to be just links, in case the link dies, but I'm not sure what else to say about an online calculator: If the link dies, there's no calculator to use)

• I must find any formula(s) or tools. What I need is the entrance and exit time to the dark side of the Earth. Commented Jul 26, 2018 at 18:15