There are many cases, especially with galaxies, that adding narrowband to an RGB image is beneficial. The hydrogen-alpha narrowband will help show some of the hydrogen-dominated sections of galaxies. Once we’ve combined our red, green and blue images into a single RGB image, we can enhance the red with Hydrogen-alpha by using the NBRGB Combination script.
PixInsight includes a script called NBRGB Combination (Scripts – Utilities – NBRGBCombination).
Select the source RGB image and select the HA image for the R channel. For the HA image, you ned to set the bandwidth (nm) number for your filter. The most common ones are 7nm and 3nm.
Once setup, hit the NBRGB button to verify the results.
As you can see, adding HA to this galaxy image brings out the hydrogen dominated regions significantly.
The next step is to run through some color calibration processes.