To add to Wes' thoughts - Most DSLRs do not have any amp-glow. That's because most of the read-out circuitry isn't integrated into the imaging chip. Contrast that with the CMOS chips in dedicated astro-photography cameras. Most of them are intended for security cameras, where compact design and low-light performance is critical and trumps image quality. They're also typically designed for video, with relatively fast frame rates.
Combine those design goals, and the CMOS sensors we use have read-out circuitry integrated into the chip itself. The read-out circuitry generates amp-glows, and the amp-glow gets larger as the exposure time lengthens. That's not a problem for the intended use of these chips where the exposure times are very short. But for our purposes, it's significant. If you can hold the temperature of the sensor constant, then you can calibrate out the amp-glow with an identically matching exposure dark-frame. But the key is "hold the temperature constant", which you can't do with an uncooled astro camera. So these cameras work quite well in the uncooled version for planetary imaging where exposure times are very short. Not so much for long-exposure DSO photography.
The same problem is present in DSLRs, but not to the extent of surveillance-chip astro cameras since DSLR chips don't typically have amp-glows.