Now, I'm in the process of learning astrophotography it has been quite the learning curve. A huge help has been using a guide camera that can track and correct the main scope while it is imaging. The Orion guider works very well for this, if your scope has the proper connection for it.
If you don't have such a port or your scope does not have tracking ability, your kinda screwed. A decently aligned equatorial type platform with guiding can help cover a multitude of problems. If you running in alt-az only, then you will be severally limited to no more than 25 second exposures before image rotation sets in.
One thing about DSLR's used for astrophotography, is shutter life. For "normal" usage a shutter will last a life time (about 100,000 cycles. For astro work, that 100k number can be blasted through in a year or two. Using a flip mirror system to frame and focus the camera is a great idea (use one myself) but also, see about getting a cheap CCD imager off of Astromart. I got a cheap Orion StarShoot II for $150, just to learn on and not wipe out my XTi shutter. Don't expect any great results with a cheap CCD astro camera, but it gets you used to the drill it takes to do decent astrophotography. I figure I'm nearly done with the basics and just ready to move up to the DSLR, later this summer.
Just take your time and learn each step in the process. It is a long steep learning curve, but once you get over it, the rest is actually pretty easy.
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