The Crescent Nebula NGC 6888

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Stefan B
Posts: 46
Joined: Sat Oct 31, 2020 8:59 pm

The Crescent Nebula NGC 6888

Post by Stefan B »

With the help of @RICH-DSO (thanks so much again!) with ASTAP and aligning differenct channels I was able to do a combination of duo narrowband data in H(HO)O and RGB stars from broadband data of the Crescent Nebula:

Image

StarTools did a great job on stretching the data (auotdev without ROI) and revealing the details (applying deconvolution and seeing the result has been a nice moment :-)). I can't stress enough how much I love 1.7's new SuperStructure module! It made a huge difference for the final result.
Combining the narrowband and broadband data in the layering module was fine, but I had to fiddle a bit with the star mask for the brighter stars with spikes. The algorithm sometimes has problems with isolating the stars and their spikes. Moreover, in the mask module the preset 'fat stars' was greyed out...does this one only work with tracking activated?

See details here: https://www.astrobin.com/qmf2bj/?nc=user

Regards
Stefan
Carles
Posts: 67
Joined: Thu Jul 30, 2020 5:06 pm

Re: The Crescent Nebula NGC 6888

Post by Carles »

Awesome work, Stefan!

Did you use layer module straight? using compose to merge RGB with HO(o) wouldn't work?
I wonder as I'd like to get an l-enhance or l-extreme at some point... :)

Carles.
Stefan B
Posts: 46
Joined: Sat Oct 31, 2020 8:59 pm

Re: The Crescent Nebula NGC 6888

Post by Stefan B »

Hi Carles,

my workflow looked like the following:
- load the l-eNhance data into R, G and B in the compose module and use the bi-color/OSC option
- autodev, crop, wipe, autodev
- going through the modules (color: H[HO]O), final denoise and save

- load the broadband data (NOT using the compose module)
- autodev, crop (the exact same crop like for the l-eNhance data), wipe, autodev (a very basic one since I didn't want to extract detail, but only color; moreover, I didn't want to bloat stars since then the color would be gone)
- no processing in the different modules
- final denoise and save

Then both images were loaded in the layer module, a star mask on the l-eNhance image with the reduced stars was applied and the color of the RGB image was inherited to the l-eNhance image. The composite contained the H(HO)O image with RGB stars. Does that make sense?

I would not know how to get the RGB stars into the image by using the Compose module. Do you have an idea?

As for the point of getting an l-eNhance or l-extreme filter. I definitely don't regret buying the l-eNhance. With an OSC or DSLR it is a good way to enhance contrast and SNR on nebula targets (this probably also holds true for different duo/tri/quad band filters of other manufacturers). As far as I know you are using a dedicated astro camera and are dealing with more light pollution, right? (I am in Bortle 4) In this case I would go for the l-extreme to exclude more of the light pollution. But with my old, not very sensitive DSLR I was worried that with the l-extreme I wouldn't see anything in short exposures which would make framing and focusing more difficult. Moreover, I feared that I would have to go beyond 5 min of single exposures for gaining enough signal which would heat up my uncooled sensor. Nothing of this should be a problem for you. Just my 2 cents...I never used the l-extreme myself ;-)

Best regards
Stefan
Carles
Posts: 67
Joined: Thu Jul 30, 2020 5:06 pm

Re: The Crescent Nebula NGC 6888

Post by Carles »

Hi Stefan!

thanks for sharing your workflow! :D
it looks interesting, and result is good :=)

Umm I was thinking on merging R with Halpha and B with Oiii from L-enhance;
open L-enhance file in compose only in R and save the file as Halpha
Open L-enhance file in compose only in B and save as Oiii
split the RGB (open the RGB file in R- save . G --save, B --save. )

merge Red with H-alpha (compose-> open Red in Red and H-alpha in Green) save as R+halpha
Merge Blue with Oiii ( Compose -> open Blue in Blue and Oiii in Green) save as B+ Oiii

then again in Compose module, load R+Halpha, Green, and B+Oiii.

I don't know if that would work right as I don't have the l-enhance files to play with. but maybe could work

this way you'd keep the star colors since you're still using RGB and also get stronger signal of the Halpha and Oii in
the red and blue channels.

Although, it is a lot of work!! haha if you give it a try let me know! :D


the other option is using L-enhance data as a Luminance in Compose, then color data in R,G and B.
like @ldipenti used in this post viewtopic.php?p=9963#p9963

I really like his result too :D He's using L-extreme, but should be similar with L-enhance.

and I think you're right; I should go with L-extreme, Since i am in Bortle 7...or worse because have many light
around (even checking in apps like Clearoutside states bortle 6...is not really)

Regards

Carles.
Stefan B
Posts: 46
Joined: Sat Oct 31, 2020 8:59 pm

Re: The Crescent Nebula NGC 6888

Post by Stefan B »

Hi Carles,

thanks for your suggested workflow! I think that should work and yield pretty natural colors. But if I do an H(HO)O recombination after splitting and recombining all the channels, false colored stars would be result, right?

If I'd like to use true colors for DSO and stars I'd go for the l-eNhance=luminance and broadband=RGB option you mentioned. I already tried this on the Flaming star nebula:
Image
Using the same data I already tried different workflows and color combinations, comparable to @ldipenti:

viewtopic.php?p=9570#p9570

If you have one of those duo narrowband filters and tried your suggested workflow please let me know the result! :-)

Best regards
Stefan
Carles
Posts: 67
Joined: Thu Jul 30, 2020 5:06 pm

Re: The Crescent Nebula NGC 6888

Post by Carles »

Hi Stefan!

that is also an excellent result!!

unfortunately I don't have any of those filters ( I want them, though! ) So can't test it myself.

But as you mention, if you set the palette to HOO... I am not sure. It all would depend maybe on the settings in Colour module?
Perhaps if mask out the stars and set the identity to HOO , keep, then invert mask so the white balance keep the stars to their natural colour?

Not sure if could work (that is, loading it from compose as mentioned ) But I assume at that point it will only be a reinforced Red channel ? or will it take as H-alpha ? no idea!

Very interesting thread that one, too! Thanks :D

Kind Regards

Carles.
Stefan B
Posts: 46
Joined: Sat Oct 31, 2020 8:59 pm

Re: The Crescent Nebula NGC 6888

Post by Stefan B »

Hi Carles,

protecting the stars with a mask from being H(HO)O rendered and afterwards only balance the colors of the stars might work. Maybe I will have a go at this with the next suitable data set I get :D

Best regards and clear skies!
Stefan
Carles
Posts: 67
Joined: Thu Jul 30, 2020 5:06 pm

Re: The Crescent Nebula NGC 6888

Post by Carles »

Hi Stefan! :D

ok!! I'll be looking forward to see what results you get! ^^

Clear skies!

Carles.
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