This is a superset of the data in my earlier HOO image. I added some SII data and decided to process it as an HOS image though I looked at in a bunch of different palettes before deciding. What pushed me toward this one was that by keeping the h-alpha in red, the image had at least one basis in reality though I liked some of the other combinations.

I also tried a new technique here. My intent was to process it using a tone map method but I couldn't control the noise well enough for that to look good in the final result. But, since the new PixInsight release had the starnet process built in (it hadn't been able to run on the Mac for a while), I tried an idea I had been toying with. The intent was to extract the stars and the nebula and process each separately and then recombine at the end. Mostly it seemed to work though there are two drawbacks. On the plus side, you can control how prominent the stars are directly and not need to shrink them later.

Process for the Ha master:

- dynamic crop

- mure denoise

- automatic background extractor

- create a clone of this and call it stars

- perform a moderate HT stretch on the ha master (only change mid tones!)

- run starnet and have it make a star mask

- revert the HT stretch (1-mid tone value from earlier stretch)

Here was my process for the OIII and SII masters:

- dynamic crop

- mure denoise

- automatic background extractor

- linear fit to Ha master

- perform a moderate HT stretch on the ha master (only change mid tones!)

- run starnet (no need for mask)

- revert the HT stretch (1-mid tone value from earlier stretch)

Use the same mid tone stretch value for all three stretches to maintain color balance. It's important to not change the black point. The original stretch is fully reversible only if the black and white points are left unchanged.

On the stars image:

- use the mask from the Ha starnet process and invert it (so it protects the stars)

- use pixel math to set the image to 0

This will remove everything but the stars.

For the nebula:

- channel combination (Ha, OIII, SII)

- MLT noise reduction

- HT stretch

- Curves (contrast, color)

For the stars:

- HT stretch

Next use pixel math to combine nebula with stars using max().

Then a final contrast tweak with curves.

I did have to use a mask to give the star 52-Cygnii (the big one in the veil) an extra stretch to hide an OIII halo that starnet left in the nebula. It's not ideal and looks a little odd but less odd than the green circle that would have been there.

The two downsides I see to this are dealing with artifacts like I just described when a halo is in the nebula and this effectively makes all the stars appear in front of the nebula when, in reality, some of them must have been shining through the nebula.

This also loses all star color since you just have the stars from the Ha frame but star colors in narrowband images can be distracting so you could view that as a pro or a con depending on your view.