Soul Nebula

[Stefan B]

While the weather of winter and spring of 2022/23 has been really bad for imaging the weather since solstice was really generous... So I got the opportunity to turn to a bright emission nebula in the last couple of days. Or so I thought. I had imagined that the Soul Nebula wouldn't be so faint. I am wondering how all the images with these sharp details of faint structures are achieved. There are pictures with this from before the BXT era so it can't be just that...anyway, I tried to get a natural looking image with colorful stars and I think that turned out okay.

See https://www.astrobin.com/z40wlf/ for technical details.

SVD lacked the punch this time but this might be anticipated since I blended broadband and duo NB before SVD so the PSFs were probably a mess.

Regards
Stefan

[Carles]

Hi @Stefan B

Nice image! although, with 13h of L-enhance, i would have expected to see the nebula more prominent. Could you show the l-enchance file stretch even in BW ? Wonder how much signal is there in comparision of the final image. Also, you could try to stretch/process that Narrowband file as BW (in compose just load the file as L, R, G and B but keep it as Mono) , then use as "luminance" layer on Layer module ; in optios, you would choose "Colour of Foreground" so it would remain the luminance of the NB file, with colour of your final RGB file. Try it out

Carles

[fmeireso]

Great image Stefan nonetheless.

It is rather faint imho, so is the Heart allthough i think IC 1848 is brighter then the Elephant trunk imho.

You succeed in getting some OIII out in blue.
I am also working on that object but i stumbled onto an issue. In APT i have a hard time stretching an image. It is hardly visible so i messed up a bit the framing. I have 2h48 min of data also with the L-enhance but the nebulosity came out quite while. This i guess i will just have to redo it for better framing and more integration time...

[Stefan B]

Hi Carles and Freddy!

although, with 13h of L-enhance, i would have expected to see the nebula more prominent. Could you show the l-enchance file stretch even in BW ? Wonder how much signal is there in comparision of the final image.

Yeah, I had the same impression. It's surprisingly faint. Please have a look yourself and play around with the data:

UV-IR: https://www.dropbox.com/scl/fi/9k1pka5s ... 74jya&dl=0

l-eNhance: https://www.dropbox.com/scl/fi/f5aypkrd ... fdb1l&dl=0

The stacks are already aligned.

Also, you could try to stretch/process that Narrowband file as BW (in compose just load the file as L, R, G and B but keep it as Mono) , then use as "luminance" layer on Layer module ; in optios, you would choose "Colour of Foreground" so it would remain the luminance of the NB file, with colour of your final RGB file. Try it out

Well, that sounds like a complicated process when I could just insert the l-eNhance stack into the Luminance and the broadband stack into the RGB slots in Compose and choose "L, RGB"

I often tried that and compared it to NBAccent. I always prefered the NBAccent rendition. The problem is that duo NB luminance and broadband chrominance don't match nicely. The l-eNhance data has bright pixels with a certain color where the broadband data just has neutral background. So you end up with a bright grey pixel when you only use the duo NB brightness without color But it might be worth a try here.

You succeed in getting some OIII out in blue.

Kind of. Limited by the Ha/OIII ratio. And Ha is just overwhelming like most of time.

I am also working on that object but i stumbled onto an issue. In APT i have a hard time stretching an image. It is hardly visible so i messed up a bit the framing. I have 2h48 min of data also with the L-enhance but the nebulosity came out quite while. This i guess i will just have to redo it for better framing and more integration time...

More time always helps, not only with detail but also with color. Framing for me is basically a no-brainer when I stand next to the scope since I use NINA and determined the coordinates and the rotation in the Framing wizard beforehand based on a deep sky image of a NASA survey. Quite handy.

Wishing you luck with your Soul nebula image!

Regards
Stefan

[Stefan B]

By the way, this time I used the Scientific approach in Color. Came out fine I think. Artistic looked pretty boring and colors washed out.

Stars are bit bloated/haloed. I THINK I know what's causing this. None of the three nights was forecasted to be clear and there were probably clouds around. For the broadband data this was obvious in the star count of the single subs. I selected the subs aggressively but that might be blurring the stars nonetheless (and the nebula of course also).

Regards
Stefan

[Carles]

Hi @Stefan B ,

Thanks, I will play a bit with your data, thank you for sharing

The reason I'm surprised, is because I have made last year a mosaic of 2 panes of Soul Nebula with L-extreme on my Bortle 8 sky.
Folling my pre-process workflow for NarrowBand data, here's what each one looks like. Since is Bortle 8, Oiii is very faint on the single file, but it pops out nicely on final image.

By the way, this is only 3hours 20min each pane with l-extreme

split.png (311.97 KiB) Viewed 15332 times

Don't mind much the colour, can always change hue or temperature, but signal, there's plenty... So it is not actual faint nebula, I think.

Well, that sounds like a complicated process when I could just insert the l-eNhance stack into the Luminance and the broadband stack into the RGB slots in Compose and choose "L, RGB"

haha , sure, but for my tests, result doesn't get as close to what i've posted. And there's 13hours of Narrowband data.. with better skies and bigger telescope (mine 89Ed yours 150 newton ) so, we should be able to extract more signal for that

going to test your files and see what I can get

cheers,

Carles

[Carles]

@Stefan B

So here's what I got.
Loaded l=l-enhance file R=L-enh. Processed it and saved as halpha. Mono
Loaded L=lenchance G=l-enchance B=l-enhanced, processed and saved as Oiii mono
Loaded IR-uv cut as open only, processed quickly and saved as RGB
Compose L=halpha , R=halpha G=oiii B=oiii save as HaOiii mono

4in1.png (456.82 KiB) Viewed 15330 times

Compose
L= HaOiii R=Halpha G=Oiii B=Oiii
Go straight to Color -- Change to Artistic, increase dark saturation. no need to change anything
Then straight to Layer, open your RGB file and choose Color from FG as screenshot

latyer.png (395.64 KiB) Viewed 15330 times

and result this

HORGB done.jpg (474.01 KiB) Viewed 15330 times

It sureley can be refined, with use of other modules, or more work on each file, as I did it quickly and bin 50% .
The whole thing took me around 40min .

Let me know what you think.

Carles

[fmeireso]

Hi @Stefan B

Nice image! although, with 13h of L-enhance, i would have expected to see the nebula more prominent.

Carles

I played a bit with it. Looking at the L-enhance stack there is alot of nebulosity in, more then Stefans picture shows actually

[Mike in Rancho]

Stefan I think that looks appropriate, other than maybe a green tint to a couple of the yellow stars?

The star field in general looks great to me though. Such beautiful coloring.

The target falls into a few of those that I don't particularly like - Heart, Soul, Elephant Trunk (except in SHO). I sound like a grumpy old man. You rotten DSO's get out of my sky!

They are faint, not bad in Ha, but poor or overlapping in other emissions. The ST philosophy of relative emissions thus often makes for unappealing images because so much Ha throttling is often needed. The result tends to be weak Ha, weak Oiii, and a whole lot of blueish-gray fog.

Fiddling with the Style, LRGB emulation, and all the sats sliders can somewhat ameliorate this, but only so much in my experience. And the forums here are filled with such Souls/Hearts in our gallery.

You kind of just have to live with it as the way these targets are, or employ some trickery. Yes on the internet you can find Souls and Hearts with deep pools of blue and strong red all over even before BXT. Masks. Foraxx. Conaxx. Or NB combination/normalization which boosts the Oiii but throws a different s-curve at it to suppress the extra noise in that channel. I'm less against that than I am the other options, and similar results could be (sort of, ST still wants to do its thing) obtained via separate processing. Mono is more helpful here than duoband or extracting, I think, if one wants to ditch relative emissions.

Carles may have been trying something to that effect? I will have to take a closer look later or on the weekend. One thing I'm not sure of Carles is the use of the L slot in compose. I don't see a reason for that which couldn't be accomplished identically with the exposure sliders. That's all synth L does, of course - I believe the default weighting is 50% to L and 50% to RGB. Which can then be modified by the sliders if you want to re-weight your balances in the synth L creation.

[Carles]

Carles may have been trying something to that effect? I will have to take a closer look later or on the weekend. One thing I'm not sure of Carles is the use of the L slot in compose. I don't see a reason for that which couldn't be accomplished identically with the exposure sliders. That's all synth L does, of course - I believe the default weighting is 50% to L and 50% to RGB. Which can then be modified by the sliders if you want to re-weight your balances in the synth L creation.

@Mike in Rancho

Right, but if you add L in compose slot, and also you increase L slider, you'll see more weighting on it. Try it and you'll see. Now, what's the theory behind this? No idea, I just tried it and it works, in the same way, decreasing G or B, to balance the temporary color result in Compose, that it will not, at all, be the result going to Color module with "auto Scientific " balancing.