Here are my first attempts at imaging with my ‘new’ Borg 200 mm f/3.8 astrograph, the same model RickS started using recently. I say ‘new’ because I acquired the Borg back in autumn 2017, and have only just recently had a go at processing the first two data sets. It took quiet a lot of experimentation interchanging the various tubes until I found a backspacing near to the sweet spot for flat images with circular stars in the corners. The image quality seems pretty damn good to me. I think the Borg is a winner.
https://flic.kr/p/2c1UGNc
https://flic.kr/p/RgK4fs