There is lots of software that can display what the sky should look like at any given time and terrestrial location. I have also heard that spacecraft determine their position based on pictures they take and then matching stars to it, called star tracking as far as I was able to find.

Essentially what I am looking for is a star tracker like on space craft, but on earth. Is there a word for that? When looking for "star tracker app" or "star tracking smartphone", I get software that overlays the sky over the camera feed based on a wonky internal compass (not matching stars in the camera feed) or hardware that controls a telescope (I'm not looking for hardware controls). The device location and time can be determined with GPS, the only unknown is the direction the camera is facing. What is the correct term for software that does star catalog matching?

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    $\begingroup$ Interesting question! The function of matching an image of stars to the known sky is discussed in answers to How (the heck) does Astrometry.net work? (spoiler alert: "asterism matching") but to the question What this kind of software is called? hmm... dunno! $\endgroup$
    – uhoh
    Feb 18 at 22:15
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    $\begingroup$ It's called plate solving. ASTAP and Astrometry.net are some examples. $\endgroup$ Feb 19 at 6:03
  • $\begingroup$ @GregMiller that should be an answer, if it'll let you post one that short. It's better than mine. $\endgroup$
    – Erin Anne
    Feb 19 at 8:54

2 Answers 2


You're looking for a "plate solver". Astrometry.net is probably the best, but others like ASTAP and Match exist. There are many open-source desktop plate solvers too, most of which use Astrometry.net under the hood.

"Star Trackers", such as OpenStarTracker or LOST (which I'm the developer of), are generally not as good as Astrometry for identifying pictures on earth, as they're designed to identify pictures on resource-constrained satellites. For example, LOST's database can be as small as ~150KB, while Astrometry's, I believe, is multiple gigabytes. Star trackers are fast, use small databases, little memory, and might be able to identify certain images with few stars in them that other plate-solvers fail at.

However, open source plate solvers today are simply higher quality software than open source star trackers, as the plate solvers are much more popular. Plate solvers are also great at solving images with much longer focal lengths (much more "zoomed in"), such as those taken through telescopes. That's because most star tracker catalogs only include stars visible to the naked eye, while plate solver catalogs include many more astronomical objects.

Further, plate solvers can usually work even if they don't know the camera's parameters, while star trackers tend to require one to know their camera's focal length quite precisely.


Unfortunately, "software star tracker" is also as close as I've gotten so far. It's how OpenStartracker refers to itself. Lost-in-space star identification algorithms might also get you somewhere, but results like this technology transfer program Low Cost Star Tracker Software don't seem to have a lot of additional key words to look for.

I tried searching for "asterism matching" per uhoh's comment but "asterism" seems to be more polluted as a search term.


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