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 and without them it would be a very different hobby. Putting the fancy optics and mounts to one side for a moment, it is a full understanding of the sensor and how it works (or not) that shapes every imaging session. We know that astrophotographers take many exposures but two key questions remain, how many and for how long? Unlike conventional photography, the answer is not a simple meter reading. Each individual session has a unique combination of conditions, object, optics, sensor and filtering and each requires a unique exposure plan. A list of instructions without any explanation is not that useful. It is more valuable to discuss exposure, however, after we understand how sensors work, the nature of light and how to make up for our system’s deficiencies. Some of that involves the process of calibration, which we will touch upon here but also has its own chapter later on. The discussion will get a little technical but it is essential for a better understanding of what we are doing and why.
