I can't find the exact answer in Baidu, so let's ask, please tell me how the astronomical black-and-white frozen ccd takes dark and empty photos, which can be more detailed.

CCD is easy to produce thermal noise at room temperature, and cooling to low temperature can reduce thermal noise. Cooling is of course to prepare for long exposure. Ordinary cameras shoot for more than 30 seconds, and the noise will be messy. Astronomical cameras can shoot at the target for a month continuously, so heat dissipation is very important. The photos of astronomical cameras are post-synthesized pseudo-colors, which are synthesized by taking single-spectrum photos of different spectra. Each shot needs a different filter, so only gray images are needed.