This scheme illustrates the essence of image stacking. With image stacking, you have combined all your light frames (the actual images of the sky) into a single image with an enhanced signal-to-noise ratio. What Histogram Stretching Is And Why You Need It Of the steps mentioned above, it is worth to spend a few words on the Histogram Stretching, as it is of utmost importance in deep-sky astrophotography. In astrophotography, the post-processing includes steps that are crucial to the quality of the final image. 4) Conclusions What Does Post-Processing Mean In Astrophotography?