An example of full frame OSC imaging on a F/3,9 Astrograph.
(highres on Astrobin:
http://www.astrobin.com/full/90416/0/ )
Imaged with a Canon 5D Mark III (Unmodified) and a Orion 8" Astrograph F/3,9, Celestron Cgem Dx. SSAG & PHD guiding
Read more about the acquisition details on my blog:
http://www.astrotanja.com/reflection...3-and-friends/
Also how shooting flats greatly improved the vignetting. I shot my flats the day after using an LCD display indoors. Here's a very easy and helpful article from Cory Schmitz on how you can do them
http://astroshake.com/2014/02/howto-...rophotography/