In preparation for my first astrophotography trial using 100% Linux based software, I added a couple of important filters to KStars FITSViewer tool. The first filter Equalize performs histogram equalization which enhances the contrast of an image. The filter works quite well with images of diffuse continuous flux such as nebulae or galaxies. For star fields, the filter actually significantly raises the background noise level, and stars become buried within the noise. Here is an example of applying the Equalize filter to M42. As you can see, the contrast of the image is greatly enhanced.
|M42 before Equalize filter|
|M42 after Equalize filter|
|Star field before Low Filter Pass|
|Star field after Low Filter Pass|