Starguide - A Practical Guide to Astro-Photography

A simple method to edit the structures and colors of e.g. nebulae without influencing the image of the stars is to split the stars and the nebulae into 2 separate images. This also has the advantage that the stars can be processed separately, e.g. to intensify the colors of the stars or to reduce the number of stars if they are present in excess in the image and impair the overall impression.

This can be easily done in PixInsight using StarnetV2. 

The post-processing of the Veil Nebula (NGC 6960 - ObservationID: 0153) can serve as an example here. In the original image, the nebula was barely visible because of the many stars; this was only improved by splitting the image into the nebula and the stars.

To learn more about the PixInsight AddOn installation, see the StarnetV2 article in this document.

Steps

1. Apply the StarNetV2 process on the source image and let StarNet2 create a star mask
   
2. Rename the identifiers of the 2 resulting images to e.g. "Stars" and "Nebula"
3. Apply Curves Transformation and Histogram Transfer to stretch both images, e.g. to reduce the number of stars on the "Stars" image
4. Use PixelMath to re-integrate both images into one final image

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