Image stacking is a collection of related techniques used in astrophotography which all use multiple images taken by a camera to achieve a more detailed photo than would otherwise be possible. I’ve talked about image stacking in the past, but I hand-waved the statistical parts a bit. In this post, I want to dig into those mathematical details so that you understand why image stacking actually works.
But first, I’ll tell a story about thermometers. We’ll come back to image stacking after that.
Let’s imagine you’re a scientist, and you need to know the temperature of the room you’re in to within a tenth of a degree in order to run an experiment. You dutifully order a super expensive NIST-traceable thermometer online, but on the day it arrives, you open the box only to discover that you got a hundred cheap alcohol thermometers instead.
The expensive thermometer would have done the job to within a hundredth of a degree, but now it’s too late to wait for a new one to arrive, and all you have are these che