Plate solving image with a 50mm lens

Hi all, I have been happily using SGP (currently and plate solving using a verity of scopes and PlatSolve2 for years. Recently I decided to try wide field using a Canon EF 50mm 1.8 II and QHY168C. I captured an image (see attached) and uploaded to which showed a pixel scale of 19.1 arcsec/pixel and size of 26.8 x 17.8 deg. I fed this into All Sky Plate Solver which solved in under 60s and stated a Focal Length of 51mm.

I then configured a new profile in SGP setting the camera scale to 19.1, scope FL to 51mm and aperture to 50mm. I then tested with PlateSolve2 and max regions and it would not solve. When it failed over to a blind solve it did solve and sync.

Using stand alone PlateSolve 2.28 I matched the same image in seconds - see other image attachment.

Is this an issue with the scale of the image I am trying to solve or have I got the settings wrong?

Many thanks in advance for any support you can offer.


Try ASTAP solver, its faster and more reliable than PlateSolve2.
PlatseSolve2 did not for me and ASTAP never gave me a problem with any focal length.


Surely if your FL is 51mm and your f/ratio is f/1.8, your aperture is about 28mm?