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

[dx_ron]

I thought I might join Mike on his Sh2-115 journey, but a few subs showing how faint that is scared me off. So, I spent what little decent imaging time I had the last month on the Propeller (conveniently located in the same neighborhood). Those DWB and Simeis catalog designations are a couple of mid-20th-century catalogs, with DWB being specific to Cygnus Ha regions.

The Propeller shares one trait with Sh2-115 - there's darn little Oiii yet many people show a bunch of blue in their SHO images. With my duoband filter I didn't even try to bring out Oiii. The full-mono itch grows stronger... Luckily there's a billion-dollar lottery drawing coming up!

Shot with the AT130EDT + 0.8x reducer, Risingcam IMX571C. The odd aspect ratio is user error (forgot to check rotation angle for the OSC subs ). I might re-do the OSC, there's only about an hours worth anyway, but the cropped framing fortuitously accentuates the propeller shape. Just under 10 hours worth of AlpT duoband.

I'll try most anything to avoid the hassle of making a star mask needed to gracefully layer in star colors, so I tried the trick of duoband as L, RGB from OSC and duoband as NB Accents. If that's totally violating the spirit of ST, I promise to stop.

My astrobin account is temporarily lapsed. I will re-up, of course, but I'll do so sooner if anyone asks for better resolution. I should go back and rgb-align the OSC stack at some point.

Propeller_AlpT-as-L_+OSC_118x300+130x30_v1_700k.jpg (681.19 KiB) Viewed 1423 times

[Stefan B]

Very cool image with lots of signal! Cygnus never gets boring. And I didn't know that the Simeis objects are all in Cygnus...interesting.

I tried the trick of duoband as L, RGB from OSC and duoband as NB Accents.

I've never been lucky with this workflow. Somehow it never worked out for me but I can't recall exactly what it was...

Here it might make sense to visit HDR or contrast (with bumping up locality) AFTER NBAccent in order to get a better view on the propeller. That's definitely not in the spirit of NBAccent but in my experience it reduces the look after NBA which is sometimes a bit washed out.

Colorwise there seems to be quite some OIII hidden in the data, indicated by the white color where Ha and OIII probably overlap. Maybe that can be better differentiated in Color or NBA. Maybe also trying to use the usual workflow with broadband in RGB and duo NB data in NBA slot might be worth a try?

If you like, you can share the two stacks. Weather is terrible here so I'd love to give it a try and do some processing

Regards
Stefan

[Mike in Rancho]

Cygnus. So very red, and often so very faint.

Definitely a nicely-visible propeller in there. Though if I was going to stick one in front of a plane, I think it would be M13's version.

I think I remember a thread with Freddy and a few of us a while back, and I thought the ultimate conclusion was that NB as both L and NBAccent would not work out right. Or at the very least you would not get any advantage from it.

Also the ills of using NB as L against RGB/OSC chrominance have been discussed ad nauseam, particularly as to warping of proper color balance and just plain pinkification of everything.

A more normal OSC with NB Accent workflow, possibly with extra saturation in Color to overcome any washing out in the NB Accent (masked reversal is difficult in heavy nebula), might retain better RGB stars and still have strong red/white nebula?

Though Stefan and I were also just talking about the see-saw band slider in NB Accent and just ST's relative-only narrowband in general, too.

[decay]

I think I remember a thread with Freddy and a few of us a while back, and I thought the ultimate conclusion was that NB as both L and NBAccent would not work out right. Or at the very least you would not get any advantage from it.

Yepp, I guess it was this discussion:
viewtopic.php?p=13756#p13756

-> "I would not use both Ha for luminance and the NBAccent module, as the luminance and NB accent stretch will differ and will interact incorrectly, causing reddening/modification of other areas as well."

Hope it helps, Dietmar.

[dx_ron]

I didn't know that the Simeis objects are all in Cygnus...interesting.

That's because it's not true... Oops (editing my original post)

I will try a couple of alternate approaches. One obvious one is to simply restrict the ROI in Optidev to the propeller only. That should be similar to some abin images that push the surrounding Ha into the background.

As far as Oiii goes, the abin images tend to show a ton of blue surrounding the 'upper' half of the propeller, as in https://www.astrobin.com/9p16r0/C/

I suspect, as with Sh2-115, that involves suppressing Ha / boosting Oiii with some sort of mask, because there is quite a lot of Ha signal there.

[dx_ron]

I tried some quickie Bin/Crop/Wipe/Opti/Color with various ways of loading the data and just grabbed screenshots to get a sense of the overall look and feel.

Duoband as L, OSC in RGB (no NB Accents file):

dou-as-L.jpg (343.86 KiB) Viewed 1349 times

OSC in RGB, duoband as NB Accents (the way the creator intended):

duo-as-NBa.jpg (694.96 KiB) Viewed 1349 times

This would be fine - with a crapton more OSC data. With just an hour it's a noisy mess

Plain HOO (no OSC at all):

HOO_no-OSC_1.jpg (370.07 KiB) Viewed 1349 times

As you can see, I used the pure-red Ha for the NB Accents - but I've never figured out how to replicate that with HOO processing of the duoband as everything, so I get pink.

One more image, but the forum has a 3-image limit as far as I can tell.

[dx_ron]

Finally, my attempt to "bring out" Oiii. Still with only the duoband data. I pushed Red/Ha way, way down. Then used Filter for 2 jabs of Saturate Visual Ha.

HOO_no-OSC_2_2xSat-Ha.jpg (681.53 KiB) Viewed 1349 times

This sort of replicates the general features of some astrobin representations of blue regions surrounding the upper arm of the propeller - but it's a noisy mess. And the Ha is quite pink still.

[Does anyone really think there huge clouds of pure oxygen floating around in space? How would such a thing be formed?]

I wonder if we could get the same Balmer vs Pure Red choice for duoband processing as in the NB Accents module?

The bottom line, I guess: if I want duoband + RGB stars I need to either collect 10+ additional hours of OSC data or go with the star mask / Layers approach.

[Mike in Rancho]

Interesting diversity of images, Ron.

Aesthetically, I like image 1. Much more field-filling of the nebula, and the whitening regions help the propeller shape stand out. But, with a duo being used as L against RGB coloring, then ramped again I guess in NB Accent, I'm not sure what it all means (if anything).

The next set of three seems to be what would be expected, though I think more and stronger might be possible in the normal as-intended NB Accent version? That one is the winner of those three to my eye, though I would like a little more whitening from the OIII component.

The HOO is also as we are used to - blue/gray fog from so much Ha throttling. Granted as you say, in most cases where there is OIII, there is Ha in the same spots, and plenty more of it. This seems a good example, as was my Sh2-115. I think the targets are fewer where you can find some legitimately distinct OIII.

To your question on the HOO version, I would think you could get more of the pure red if you put the saturation on blast, and/or flip the controls back to Scientific and CIE Luminance Retention (or whatever they usually are).

You could also drop gamma either post-denoise using FilmDev, or within NB Accent, which will often increase contrast and richen up colors.

I've never had much luck blending in RGB stars with a mask-color of fg when there's nebula around, and the same goes for continuum reversal after NB Accent. So there's always the approach I took for Sh2-115, and that might work here?

[Stefan B]

Hi Ron,

nice compilation of different renditions!

Personally I think the NBAccent version looks best. Adding some more data on broadband might help as you said.

Regards
Stefan

[dx_ron]

A different, sort-of accidental, version using NB accents:

star-stretch_svd_sat-153_nb_HDR_+1.15_1600.jpg (607.12 KiB) Viewed 1198 times

Loaded the hour of OSC + the 6 hours of duoband as NB accents. Instead of setting the optidev RoI around the propeller, I made a much smaller RoI that just encompassed the two brighter stars to the right of center. My intent was to try making a super-saturated OSC image a-la Mike (though when I get to the part with 'pink reversal' I'm still confused ). I went from Optidev to SVD and thence to Color. Before trying the 500% oversaturation, I set a more normal saturation of ~150%. Followed by "I wonder what it will look like if I blend in the NB Accent now?" Not all that bad, as it turns out. This is with only the 'pure red' Ha - the HA+Oiii didn't look much different at all.

I have no idea if the SVD affected the NB channel or not. I went to Contrast, but that just seemed to darken the nebulosity for some reason. I was able to apply a touch of HDR, which did impact the nebulosity (hopefully in a not too inappropriate way). It seemed to behave quite similarly to how it acts when just the duoband data are loaded. There are a couple of red stars that wind up creepily extra-red, but those could be touched up. I should more carefully compare the before and after NB Accents star colors, but perhaps ignoring the Oiii saved it from too much color alteration.