Digital Single-Lens Reflex cameras allow an entry point to deep sky imaging that wasn’t available 12 years ago. Back then DSLRs had relatively small sensors by today’s standards, terrible noise reduction, and were outrageously expensive. Today’s cameras have big fat chips, exceptionally low noise without cooling and can be had for very cheap! Canon holds the higher share in astrophotography, but there is plenty of support for Nikon as well. Sony and other manufacturers are getting more popular in the hobby, but in my experience, Canon and Nikon still have more software support for camera control than all others combined.
I ended up with a Canon T1i (500D), partly because of compatibility and because of a deal I couldn’t refuse. This was the first purchase I made after deciding to get back into the hobby and I took weeks to decide. I’d always wanted a DSLR for daytime use as well, so I did my research and was careful and patient about it. I stalked ebay for a couple weeks until one jumped out at me. For $150 (buy it now) was a Canon T1i, including an 18-55mm kit lens, 2x16GB SD cards, a charger and battery, all related cables, manuals and even a DSLR specific backpack! The camera was listed as barely used, and for once it was actually accurate. Everything listed was included, shipping was really fast, and the camera shutter had less than 7,000 actuations. It was essentially a brand-new camera. As a word of caution – be careful with ebay purchases and be ready to be disappointed. I took a chance and got lucky.
For me, the T1i fit the perfect match of price, features and functionality. Aside from the perfect deal I found, they generally sell from $175-$200 with 30,000-40,000 actuations. That sounds like a lot of wear and tear, until you understand that the life expectancy of the shutter is approximately 130,000 actuations.
I prefer to use BackyardEOS (BackyardNikon is also available) for my image capture software. When researching a DSLR to buy be sure that all the functionality you’re expecting to use is available in the imaging software you plan to use. For example, I really wanted live-view, so the lowest model Canon I could get would be the XSi, which is one step down from the T1i. For $20-$30 more on the used market, I could get a better image processor, newer chip and some other small features in the T1i. Those were the deciding factors for me. So, it was a just matter of hunting.
A Quick Note on Astrophotography Specific Cameras over DSLR:
I have switched to a ZWO ASI071 for my primary imaging camera. Data is cleaner, more easily processed and more quickly acquired. That said, I still think that a DSLR is the easier and more versatile way to start out in Astrophotography.
Your guide camera has one purpose in life – to lock onto a guide star and not let it go, ever. My initial thought was to use my old Meade DSI with my modified 8×50 finder scope. Just as I was finishing that build, the DSI decided that it no longer wanted that duty. The firmware seemed shot. Windows saw that something was plugged in, but had no idea what. I could still use the modified guide scope, but I needed a camera – another expense that I had to keep it to a minimum. The ASI120 is the standard for the lower end guide camera. It’s cheap reliable and produces small, round, defined stars. I’ve paired it with a ZWO 60mm guide scope and piggy-backed it to my reflector.