Thanks for the comments all.
If you were wondering how real imaging at a focal length of 300mm is, here are a couple of animated gifs with the exact same area from the ESO Deep Sky Survey.
Here
http://archive.eso.org/dss/dss
This is a 40' X 40' crop animated gif 2MB
http://d1355990.i49.quadrahosting.co...9/restest2.gif
To show the really fine detail or lack thereof 8.5' X 8.5' crop animated gif 2MB.
http://d1355990.i49.quadrahosting.co...09/restest.gif
My guess is that the resolution is better than about 20" for really dim stars. This is a bit less than four sensor pixels.
Bert