Thanks jjj. I will be using it prime on the scope of course. But I will be using it by itself first,guided somehow or other. so want a good lens for multiples on say m42 for arguments sake. I had a quick look on the net re. the 90mm macro and was mightily impressed. It always seems counter intuitive to me seeing a macro lens used for other things like portraits etc.
http://www.pixel-peeper.com/lenses/?lens=45&p=4 I think i can see which way I'll be going. 550D or 600D body with separate lens. There'll be more lenses later but which one for starters. Do you use zoom at all when imaging nebula's and suchlike? For instance jjjnettie, how much zoom on that cool pic of Antares.