M20 is a the rare one that looks good in narrowband or broadband and is bright in all 7 filters.  It has all the elements of emission, reflection and dark nebulosity.  Another oddity is that, thanks to the enormously bright stars it is birthing, the nebulosity is so bright I can see it in my masters before stretching.  So the challenge is representing all of these features at the same time and compressing range of brightness while still conveying the center as very bright.  

I shot all 7 filters with no idea how I would use them or if I would use them.  For the narrowband data I produced a SHO blend and mostly processed it, and then a dynamic blend and processed that.  I liked things from each but ended up blending them both together as finished products.  The Luminance data was stretched twice, once to bring contrast and detail to the background Ha field and the other to retain contrast and brightness in the bright core.  Those two vary different stretches were combined using a luminance mask to take the shadows from the background stretch and the highlights from the core stretch.  I used the brightness and contrast tool to adjust the two layers until the blend came together.  RGB data was done with a single, conservative stretch keeping the background fairly bright to allow some color there.  I then increased saturation with the Curves tool in PI.  

The RGB and L data was combined in PS and came together pretty well.  After making my tweaks to the LRGB and SHO versions in PS I was left with two vastly different images.  The yellow-brown dust lanes in the RGB data were mostly colorless in the SHO.  The bright blue inner area was similar in both.  The background Ha emission field was a nice deep red in SHO but more washed out in LRGB.   

So I decided to try just blending both the SHO and LRGB nearly finished images as 50/50 Layers.  It came out surprisingly well!  I wanted to keep more of the SHO in the background and more of the LRGB for the nebula proper so I did a luminance mask over the LRGB allowing less background and more object data through.  In the end the Trifid is probably 75% LRGB and the background around 75% SHO.

BlurX and NoiseX were used on all masters.  StarX was also used to separate stars with the RGB stars being added back for the final version.