The sensors used are Kodak KAF8300, which are a stand-alone sensor that you hook up to a laptop. They are designed specifically for astronomy, and perform better in some ways than typical consumer cameras. DSLRs that are marketed as tuned for astrophotography often have better sensitivity to certain key wavelengths than their standard counterparts (especially hydrogen-alpha at 656nm), but are missing other benefits of 'science-grade sensors'.

"Astronomical CCD cameras are a whole different world from DSLR cameras. These are cameras designed exclusively for AP, and most offer active cooling. The nature of a CCD vs a CMOS sensor in a DSLR results in a camera that is higher sensitivity, but also higher noise. Many Astro CCD cameras have mono sensors (no bayer color layer) which means they are used with filter wheels with different colored filters to capture a natural color image. They can also be used with various narrow-band filters to capture light outside the visible spectrum."

from http://soggyastronomer.com/the-best-dslr-cameras-for-astroph...