if you are aiming for astrophotography and looking in that price range, get a decent mount and then think about what scope to put on it. If you like Celestron, the CGEPro is their best mount by far, although it is big and heavy. As others have said, an 8 or 9.25 scope might be a better bet initially, but a solid mount will last you through many scope changes.
http://www.cloudynights.com/page/art...o-review-r2502
Other mounts in that general class are the (smaller and lighter) Losmandy G11, which would be a great combo with an 8 or 9.25 SCT - or an EQ8, which is a fairly close relative to the CGEpro.