The is my first attempt at a Narrow Band image. I captured SHO data for M20, along with LRGB in April & May this year.
I feel the data were pretty high quality and after completing the LRGB image some time ago I set about the somewhat daunting task of processing the NB data. I decided to go with the Hubble palette to start with. M20 is rich in hydrogen and the Ha emissions are strong in the area where the hydrogen is being stimulated by starlight. Therefore, despite using Linear Fit, to ensure the 3 channels had the proper histogram levels for combination, the initial cut came out very, very green.....well naturally. There was also quite a bit of magenta, I guess where the OIII and Ha/ SII were emitting together. But in my research it seems that no one really likes green and magenta. So having established this blend to get to the visible spectrum, there is something of an open slather in terms of how the colours are manipulated to not have strong greens or magenta. I found that amusing. I followed a number of tutorials, which were most helpful and I came around to the benefits of shifting the colours towards more golds and blues. After all the colours are somewhat arbitrary and the aesthetics are certainly more appealing. At the end of the day, the colours and structures seen are derived from the presence in the nebula of Sulfur, Hydrogen & Oxygen, and we might as well make it look as pleasing as possible whilst appreciating the structure and complexity of the beautiful object. I hope I have done justice to it and that you find it pleasing. After a long road, I am happy with where it ended up and the detail and structure have come through very well and, at least to my eyes, it has a 3D look.
I have gone with  the starless version for a couple of reason. Adding the stars back detracts from the viewing of the nebula's structure and frankly, the pink colours of the stars in front of the nebula were a bit garish. I am still in two minds as to whether to try and fix these.
As you can see I subsequently added RGB stars using the lighten/ max pixel reading in PixInisght. This did require some manipulation of the brightness of parts of the RGB and SHO images and then restoration afterwards.
The starless version can now be seen with the mouse-over.