I’m delighted with this image of M57, the ring nebula in Lyra. I wasn’t sure I could see it at all, it’s very small compared to the galaxy targets I’ve been shooting. The ring is only about 15 pixels across in the final image but it seems perfectly clear to me. This is 11 lights at 25 sec ISO 800 shot through the Takumar 200mm lens wide open at f/4 combined with darks and biases, no flats. Processed in Siril then cropped to about 1/10 of the original. After Siril I used Paint Shop Pro and reduced brightness -15 and boosted contrast +26.
Wikipedia gives the dimensions as 230″X230″ (arcseconds) so about 4’X4′ (arcminutes) I think my camera/lens is supposed to be 2.2 arcsec/pixel so that would be only 10 px where my image is about 15px. Maybe bad focus or CA fuzziness are helping me out for a change! Jupiter at opposition is only about 50″.
UPDATE: My images are about 4.4 arcsec/pixel so 15px is 66 arcsec. NASA gives the size as 1.3 arcmin so i’m missing the red part – that’s fine.
The actual object M57 is about 2500 light years away and almost a light year across. which is around the 1.3 arcmin NASA gives.
For processing I am trying to centralize my calibration images – darks, biases, flats – and use symlinks to make Siril think they’re in the directory with the lights.