The Propeller Nebula (DWB 111 + DWB 119; Simeis 57)

[Mike in Rancho]

That's pretty darn red! Eerie looking.

Plenty of room for creativity here, but I still wonder how it would look using the workflow I did on Sh2-115.

FYI pink reversal, which could also be red/teal reversal, whatever applies, is just the layer operation using undo fg following NB Accent, with a star mask and probably a little fuzz. Discussed in some old threads about NB Accent (Dietmar could probably find them quickly!) and how the continuum Ha would add pink to many stars, and occasionally inner galactic disks/donuts, when all you wanted was the Ha knots in the spiral arms. Sometimes finding the right levels for the sliders in window 2 could help out with that, other times the reversal was the only good option.

But when there's lots of nebulosity around, even the reversal is so-so, at least as far as my talents go. As with RGB stars alone, star mask blending seems to be hit or miss.

So what I did on Sh2-115 was to first process the visual LRGB plus just the Ha via NB Accent. It was very red, and I did do a star mask reversal on that one after NB Accent. Again, not super clean on the star colors within the nebulous regions, but fair enough.

Then I processed a second time (matching crops/bins of course) but this time fed both sides into NB Accent - Ha and OIII - using the selection in compose. And that's the one where in lieu of a masked reversal, I pumped up the saturation (on the LRGB) before entering NB Accent. And in NB Accent, along with 90% gamma I weighted the narrowband file towards the OIII band balance, in order to whiten up the OIII areas (blue not being possible of course). That heavy sat helped the star colors mostly survive the NB Accent strength.

And when that was finished and saved, I then used Layer again to blend in (maybe 25%) my first image, the really red one. This helped make up for the fact that balancing in that OIII weakened the Ha into light pink or nothingness (the see-saw convo Stefan and I were having). Then later after Stefan's advice I made a little gamma/DAF reduction.

I dunno. It sorta kinda maybe gave me decent RGB stars, mostly red nebula all over, but also permitted a little lightening and detail in the spots where the OIII was. So not super pure red for everything, which I think helped.

[dx_ron]

Propeller_2023_v6_1600_500k.jpg (473.87 KiB) Viewed 1681 times

Here's where I'm at for now. I added another 45 minutes of OSC to that side of the data. Then just basic NB Accents, after experimenting with different stretches (ROIs) on the NB side and various strength settings. This is 73% strength. I blinked back and forth with undo/redo after the NBaccent module and the stars seems reasonably consistent without any special heroics. Binned 71% at the start, then another 50% bin at the end

A version with the duoband as primary brings out much more detail in the nebula, but layering in the OSC stars still looks off. This version at least preserves the distinctive propeller shape.

[Mike in Rancho]

Good combo. I think this version sets off the propeller shape the best of them all, yet still allows widespread deep red.

Star color looks within reason to me too. Maybe blinking against a visual spectrum only process could show if NB Accent is tinting them, but if it is perhaps not much. Sometimes it all works out and the stars come out the other side just fine.