re: Astrophotography
A friend of mine uses a carton tube in front of the telescope's tube to prevent humidity from obscuring the glass. (His is a G8) Mine is a 9cm and does suffer from humidity.
So, sometimes I use an A4 paper and scotch tape (but only for 1 night).
I hear the Canon EOS 300D is the next best thing for astrophotography.
But as for best pictures, it does require a very stable telescope and mine isn't quite what's required.