[teamonkey]

When processing astrophotos, multiple exposures are “stacked” together. There is a certain amount of noise in each frame - due to electronic noise or simply the random number of photons that strike a pixel in any one exposure - that you want to average out on a per-pixel basis.

However some frames may contain unwanted outliers, for example if a satellite briefly passes overhead it will appear as a very bright streak in only one frame.

By winsorizing, outlying pixel values can be eliminated while still maintaining the same number of samples per pixel as the rest of the stacked image.