The Seestar app has a Mark toggle that rings the nebulae in the frame and names the stars and constellations over the live picture. It’s pretty nice to get a quick reference on what you’re looking at, especially when sharing. Although, once you’ve used Seestar’s image processing you lose the mark and really, I just don’t like some aspects of what it shows.

The good news is that the picture still knows where it points. A Seestar frame carries a plate solution, the same numbers that let the mount find the target in the first place, and Siril can solve for that from the finished JPEG. With the pointing known, the catalogues Siril ships with drop straight onto the photo.

Since Siril can be called from the CLI, I’ve thrown together a simple python script to automate some of the pieces, add additional details from the exif data, and some little additions like a scale and compass.

The exported JPEG isn’t quite the same pixel grid as the FITS the telescope saved (the app halves the resolution and re-orients the frame), so the solve is done on the export itself rather than borrowed from the stack. That takes a couple of seconds and needs nothing from me but the focal length and the target name, which the app conveniently leaves in the file’s metadata.

What ends up on the picture

• a ring per object at its real angular size from the catalogue, not a decorative circle
• names, plus the common ones where there are any (Orion Nebula, Running Man, Eastern Veil)
• the handful of stars that have proper names
• a compass and a scale bar, both derived from the solve rather than guessed

Up close, the labels sit where they should, because nothing was placed by eye:

Another Example

NGC 6992’s 60′ circle encloses mostly empty sky, with the filament crossing its western edge. This one actually had part of the constellation Cygnus marked as well, but looks like just a line drawn through the top right since the frame doesn’t actually capture the star points of cygnus. For that I just filtered out constellations when the frame is less than 5° across.