Any addicted astrophotographer is always considering new equipment, and also debating the merits of several options. One of the most common questions for beginners is about the difference between digital SLRs and astronomical CCD cameras. I love a good experiment so below is my answer.
Both these images were taken with a Takahashi Epsilon 160 astrograph (530mm f3.3). Total exposure time for both images is 115 minutes (almost two hours). The comparison is between a CentralDS cooling modified and spectrum enhanced Canon 40D and a QHY9 astronomical CCD camera.
Through a combination of luck and good fortune, Kaz and I have three different Canon cameras - a venerable 20D DSLR, an ultra compact IXUS 70 and most recently the G9. Phil wants to know how much he sacrifices when he takes the G9 cross country skiing instead of the 20D and Kaz wants to prove that the G9 she chose to keep (after Phil won it) is really better than the IXUS 70.
Having 'upgraded' to a Hutech modified Canon 40D Digital SLR, I was keen to see how it compared to my existing Hutech 20D and what the optimum settings were for ISO and sub-exposure length. The images and results here for the 20D and 40D should be comparable with a 350D and 450D respectively since they use the same sensor.