...astrophotography.... ? I want to do some astrophotography...either prime focus with a skywatcher 80mm ed APO with a 500mm focal length or possibly a piggy back with my camera on a motorized mount and scope. My question is for the prime focus scenario...since telescope magnification is a product of the focal length of the lens arrangement and the eye piece, if I was using my DLSR in place of the eye piece, would this 500mm telescope produce an image magnification similar to that of just using my Canon 400mm f5.6L lens? This is not a "cheap lens." It uses ultra low dispersion glass and is in the $1,200 class of lenses. Mounting this lens on a Canon 20d would produce an effective focal length of 640mm with f5.6.

SO in simple terms, my question is with a camera attached to the telescope instead of the eye piece, do you get any sort of high power magnification?

I don't have either rig yet but if I can get a similar picture with my current lens then I will put more emphasis on the quailty of tracking mount and use a less expensive achromatic scope for visual gazing and alignment on targets.