I found this tutorial how to process narrowband images with Pixinsight - it gives step-by-step instructions. I wanted to try it out on my recent images of the Parrot Nebula. I did the calibration, alignment, stacking in CCDStack.
First, here is what I get with Photoshop:
And here is my first try with Pixinsight (using the color combination from the tutorial):
I like the colors of the Photoshop version better. But with Pixinsight, I could get WAY more detail and the sky looks much better too.
I asked on both the narrowbandimaging mailing list as well as the Pixinsight forum how to better color combine narrowband images. The two ideas that I received were to use CurvesTransform or HistogramTransformation.
I played with the CurvesTransform but found it very hard to manage. I could not find a way to boost the signal in one channel (red) and reduce another channel (green). But every change that I tried to make had broad heavy impact on the entire image and color scheme.
I had more luck with the HistrogramTransformation process. I could boost the red a little and reduce the green a little. Unfortunately, it had the side-effect that the background became too noisy. I tried to mitigate that by creating a mask by extracting the L component of this image and clipping the black point. With this mask, I could protect the background and apply the changes mostly to the nebula. This was the result:
Overall, I like the detail and the color in this image the most.