Why is it the best choice to use frozen ccd for deep space photography?

The biggest problem encountered in deep space photography is that the subject is too dim, so we have to often use ISO image 800-6400, and the exposure time is often tens of seconds to tens of minutes. If you have the opportunity to try to expose this kind of data, you will find all kinds of noise in the background, especially the sensors (CCD or COMS) exposed for a long time will generate a lot of heat, which is called dark current in the industry. The thermal noise generated by these dark currents will be recorded by the sensor, so that the already very weak celestial signals are submerged in the noise.

The simplest way to solve this problem is to cool the imaging system. The observatory can cool the whole camera with liquid nitrogen. Ordinary users only need to use one heat dissipation chip to cool CCD or CMOS. A fully working heat dissipation chip can reduce the ambient temperature of CCD by about -40 degrees, and even in hot summer, it can ensure the CCD to reach about-10 degrees, so the thermal noise is drastically reduced.

In addition, the frozen CCD is generally black and white, which is less than the Bayer filter in ordinary color cameras, so it has higher quantum efficiency and is more suitable for recording weak celestial photon signals. . .