M20 SHO with more data

[Benjamin (Ben)]

I managed to get more data on my accidental M20 narrowband project. All in the name of sorting out gear under moonlit skies (coma corrector back focus, first light for my new bright red moonlite CR2 focuser). The result was hampered by some rather drastic changes in orientation of some of the subs (due to adding spacers here there and everywhere) so the crop was necessary rather than chosen. Would benefit from a more distant view I think (still quite noisy) but mostly happy with the result.

Ha 5nm 70x180s, OIII 3nm 70x180s, SII 3nm 67x180s
8" Quattro f4 Carbon Fibre Newtonian
ZWO ASI 1600MM-Pro (Gain 200 Offset 50, -10º)
EQ6-R
Processed in Pixinsight

Astrobin: https://www.astrobin.com/full/9trn93/0/?nc=user

[Placidus (Mike and Trish)]

A clear improvement and a great result. Lots of excellent detail.

How did you map the colours? SHO implies red = SII, green = H-alpha, blue = OIII. But then you mentioned "a wash of H-alpha". Did you map that "wash of H-alpha" to red?

[Benjamin (Ben)]

I map SII to Red, Ha to Green and OIII to Blue so I start out with the Green/yellow/purple image with purplish and yellow stars. I then invert the image and remove Green, so the purple stars are now blue, then after reinverting and stretching I remove the green so end up with a kind of washed out orange/blue image. Using colour masks I intensify the reds and yellows and reinforce the blue. The colour masks I used in this process were starless so the stars weren’t too affected by all the manipulations.

P.S. I’ll make sure I spell out those things in future to avoid any confusion with colour and the science of it, which here is quite obscured.

[Andy01 (Andy)]

Originally Posted by Benjamin

I then invert the image and remove Green, so the purple stars are now blue, then after reinverting and stretching I remove the green so end up with a kind of washed out orange/blue image.

Nice result Ben.
I'll have to try your unique 'inversion' approach - sounds interesting!

[Benjamin (Ben)]

Thanks Andy. Inverting the image and applying SCNR to the green to get rid of the purple stars was a Dylan O’Donnell tip I think?

[Slawomir (Suavi)]

Very pleasing Trifid Ben

[Benjamin (Ben)]

Thanks Suavi. With some quiet encouragement I’m working on a repro that keeps the faith with the SHO colour palette: so [SII] stays orangey/red, Ha stay largely green and the [OIII] largely purpled/blue. Exciting to try to keep the colours representative and produce something that I like the look of.

[gregbradley]

Superb Ben.

Greg.

[Benjamin (Ben)]

Thanks Greg :-)

[barx1963 (Malcolm)]

Originally Posted by Andy01

Nice result Ben.
I'll have to try your unique 'inversion' approach - sounds interesting!

I have been playing with inversions for a while now. Easiest way to get rid of magenta stars in NB images, works a treat in PI. Have used it a couple of other times to correct some niggling colours when nothing else works.

Malcolm

[Benjamin (Ben)]

I guess my only issue with inverting and stripping the green is removing only the green in the inverted stars. A tight star might work (I always seem to
run into issues with halos and odd diffraction spikes) but I found a starless mask kept the background safely protected from the colour changes and inverted the stars nicely.

[Ryderscope (Rodney)]

Nice work Ben, a good result.

[ChrisV (Chris)]

That's very nice indeed

[Benjamin (Ben)]

Thanks Chris and Rodney :-)