I agree with Peters comments. The only issue with DSLR's is that they tend to be noisy at warmer temperatures if uncooled.
It would be worth considering one of the modified cooled DSLR options (I believe jjj uses one with excellent results) from Central DS either the CDS1100 or CDS600D, both are close to your wishlist price.
http://www.centralds.net/cam/?produc...led-eos-600d-2
You haven't mentioned a mount or any other associated hardware, 1200mm F/L is going to need good alignment, tracking and guiding. The newt will also need some sort of corrector (e.g. MPCC) to get decent images.