First light with the Pentax 645 300 mm ED f/4 lens.
http://www.astrofriend.eu/astronomy/...01-galaxy.html
Click on the image to bring up the full resolution image and inspect the corners. Look very good to me except one of the corner.
This old medium format lens is impressive. There are not many old cheap medium format lenses with ED glass elements, they are too old for that. The never APO medium format lenses are very expensive and have electronic aperature and focus which can be complicated to use in an astrosetup.
/Lars