Usually the impressive photos you see are made up of tens of 'subs' (images) taken with different filters and then stacked together.
For example you may have 20x5minute luminosity, 10x5m red filtered, 10x5m green filtered and 10x5 blue filtered. Those are then aligned and stacked together and combined to make the final image.
One guy had a single image that was made from a total of 55 hours of exposures! Then you have to select the good subs, process them etc.. so the image must have taken weeks to make. He has one advantage that he lives in the south of france with ~300 clear nights a year and runs a astro-holiday guesthouse!
My camera is actually a guide camera which is normally used to track stars through a second scope. The guide camera then tells the mount (the bit that moves the telescopes) which way the star is moving to track it. The main camera then takes the image through the main telescope.
I'm just using the mount without this optical tracking which is harder, once I get a main camera then the guide camera will move to guiding duties.
When you do try astrophotography - have a think about what you want todo, then plan to build up to a final rig, otherwise it will get expensive very very quickly. Lastly the priorities for astrophotography are:
1. Clear nights.. you will need lots and long enough to get exposures.
2. The best mount you can afford as this tracks the movement of the stars accurately. This will not be cheap even at the budget end. So put the money to this, even if it means using your current DSLR and lens for a while. For photography you divide the mount's payload by half. Fully loading a mount is fine for visual observations but will cause blurring, bad alignment and tracking in photos. Mine is "25Kg", so a max of 12Kg for photography and I have about 7Kg on it.
3. Then look at getting a flatfield telescope (ie an astrograph or telescope with field flattener). The SDP, as it's designed for photography, has an inbuilt flattener.
4. Cameras - you can use a DSLR, you can mod DSLRs, however a mono-cooled CCD will beat it hands down (just look at the lack of noise in first image - it's raw, straight from the camera after 5 minutes!)
5. Filters, wheels and gizmos.
