[rcheshire (Rowland)]

Hi Brett. The gear you have is an ideal place to start. I use a Canon 200mm f/2.8L USM II (a prime lens, as you know) on a 1000D or 5D MKII for wide field - 600mm is plenty enough for close work, for the time being.

Your regular DSLR is not going to give you the deep reds that you see (Ha). If you can live with that for the time being until you have learned the craft, you can delve into modded DSLRs or dedicated CCDs at a later date.

A mount is not entirely necessary at shorter focal lengths. A visit to the night scapes image section should convince you of that. There is some outstanding work there. Otherwise a good solid equatorial mount is advisable and there are plenty to choose from. There are lots of astrophotographers using unguided and guided set ups on equatorial mounts.

The differences that you may encounter comparing lenses with refractors will be seen in image flatness and chromatic aberration, basically speaking. If you can live with the limitations of your lenses or learn how to work around them, all is well.

For example. The best theoretical stop for my 200mm is f5.7, but I notice eggy stars in the corners - f6.3 is much improved for full frame. If I wanted only the center section and using an APS-C, F4, f3.2 is probably OK and much faster. Experientially, I get satisfying results at f6.3 iso400 - 800 with 210 or 180 second exposures - exposure time also depends on the sky - light polluted or dark site.

I would also take time to read up on dithering. It will make a huge difference to your image quality from the outset. A good habit to adopt, particularly with DSLRs.

Hope that's along the lines you intend to pursue.