I am saving good advice here

My EQ4(5) could take a DSLR with a normal lens and get around 5 minutes exposure. There are a lot of cheaper options if you use camera lens for AP (excluding big telephoto). Motorised EQ5 will do the job' date=' I think so will a motorised EQ3-2. What ever your choices the mount has to be equatorial though.

An astrotrac or the Vixen Polarie are designed for DSLR astrophotography with camera lens. However, both of them only track in RA and do not have goto. The Astrotrac when properly upgraded can be use as an equatorial mount for telescope and based on info on their site could handle a 4" APO.

I don't know about Canon lens mechanics, but I'd consider getting a 50/1.8 or 35/1.8 prime instead of using kit zoom lens. The Nikon kit lens I have suffers from zoom and focus creep, which render them useless for AP.[/quote']