ABSTRACT
Sensors, exposure, and calibration are inextricably linked. It is impossible to explain one of these without referencing the others. Electronic sensors are the enabler for modern astrophotography; without them, it would be a very different hobby. Both CMOS and CCD sensors convert photons into an electrical charge on the individual photosites and then use complicated electronics to convert the accumulated electrical charge into a digital value that can be read by a computer. The process that converts the voltage to a digital value has to round up or down to the nearest integer. This small error in the conversion is called quantization noise. Quantization noise becomes evident when a faint image signal undergoes extreme image stretching to increase its contrast. This chapter has concentrated firmly on optimizing pixel signal to noise ratio (SNR). In doing so, it tries to increase the signal level to the point of clipping and minimize the signal from light pollution and its associated shot noise.
