Paul,
Price is a bit steep for me just to do a test
Anyway, I stuck my neck in one of the dpreview threads with somebody with a 5D and D300 doing some astrophotography comparisions:
http://forums.dpreview.com/forums/re...ssage=26052387
Given its smaller pixels and less aperture lens the D300 seems to do a good job. He is going to do a same lens comparision soon and hopefully I can get hold of the raw files to do some comparisions.
Terry