OSC Optolong l-eNhance colour

Questions and answers about processing in StarTools and how to accomplish certain tasks.
firebrand18
Posts: 20
Joined: Tue Feb 04, 2020 1:43 pm

Re: OSC Optolong l-eNhance colour

Post by firebrand18 »

Another approach might be to use the l-enhance for what it was named for. Expose for several hours with the filter and use the stack as luminance data. Expose also without a filter (or an UV/IR cut) and use this as chrominance rgb data in the compose module. Not sure what result you would get. But I hope I can test this soon.
I was going to post the same query but Stefan beat me to it! Can you indeed use the L-Enhance as usual to capture a few hours of emission nebula then image the same on another night with UV/IR filter and then combine the Ha/OIII component with visual spectrum RGB to improve star color? Keen to see how this would work (keeping it scientific document worthy).

How would this be done in Compose? Load the L-Enhance stack in the Luminance File slot, and the UV/IR stack in the R, G, B File slots equally? What do you set the Luminance, Color setting to? Do you set the exposure sliders as well?

Interesting to get the team's and Ivo's sage advice. :)
Stefan B
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Joined: Sat Oct 31, 2020 8:59 pm

Re: OSC Optolong l-eNhance colour

Post by Stefan B »

I'd like to load l-enhance data as luminance channel and UV/IR cut data as RGB in the compose. Thus luminance detail would solely be based on the l-enhance data and color would be purely generated by broadband data. Star color would be as natural as possible I think. One also could lower the ISO/gain for the color data resulting in higher dynamic range. The nebula color would come from different atoms apart from excited hydrogen and oxygen, but the luminance SNR would come only from those two atoms. At least that's my understanding.

If one would like to include color data from the l-enhance stack one would need to additionally process the l-enhance stack which was loaded as a color set in the compose module (Ha in red only or OIII in green and blue also). You would then use the layer module to blend the l-enhance color into the image described in the first paragraph. But that's not something I would intend to do.

Maybe the skies are clear enough this weekend to record some narrowband and broadband data of the same target...

Best
Stefan
jackbak
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Joined: Sun Jun 14, 2015 3:38 pm

Re: OSC Optolong l-eNhance colour

Post by jackbak »

Ok Stefan, the engineer in me has to ask - how would do that with an OSC? Would you use a filter wheel with the OSC - having the l-enhance and the UV/IR cut in two of the slots? Because any other way (screwing them into the nose of the OSC) would totally mess with rotation, focus, dust spots, flats - eek!

Jack
Stefan B
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Re: OSC Optolong l-eNhance colour

Post by Stefan B »

In my case I would thread the filters into the nose of the coma corrector. That means taking the camera out of the focuser.
...would totally mess with rotation, focus, dust spots, flats - eek!
It's not different than for example taking two different sets of images of a galaxy. One set with broadband, one with an Ha filter to get the HII regions of the galaxy. Rotation is not a problem. In my case, I use NINA for plate solving; it tells me how to rotate the camera in order to get the same rotation each session (with 1 degree tolerance). Or you can mark your camera and focuser with tape to match the rotation after taking out the camera. You would have to focus again. Dust spots and flats: Since I would use two different filters (and would use them in two different nights) I would need two different sets of flats anyhow.

For the triangulum galaxy I once tried this two filter approach:

Image

Since high clouds only allowed for one hour of Ha in the second night, it didn't make much of a difference. But it basically works. Admittedly, it's more work...
fmeireso
Posts: 52
Joined: Mon Sep 28, 2020 8:46 pm

Re: OSC Optolong l-eNhance colour

Post by fmeireso »

firebrand18 wrote: Thu Mar 04, 2021 3:34 am
Another approach might be to use the l-enhance for what it was named for. Expose for several hours with the filter and use the stack as luminance data. Expose also without a filter (or an UV/IR cut) and use this as chrominance rgb data in the compose module. Not sure what result you would get. But I hope I can test this soon.
I was going to post the same query but Stefan beat me to it! Can you indeed use the L-Enhance as usual to capture a few hours of emission nebula then image the same on another night with UV/IR filter and then combine the Ha/OIII component with visual spectrum RGB to improve star color? Keen to see how this would work (keeping it scientific document worthy).

How would this be done in Compose? Load the L-Enhance stack in the Luminance File slot, and the UV/IR stack in the R, G, B File slots equally? What do you set the Luminance, Color setting to? Do you set the exposure sliders as well?

Interesting to get the team's and Ivo's sage advice. :)
What i did :

I had my OSC stack full spectrum no filters. Used flats , bias etc

I had my L-enhance stack , with appropriate flats , bias etc

Those two stacks you have to register so that they are aligned. Used Siril for that , seemed to work.

In compose then in Luminance you load the L-enhance stack
In compose r and g and b you load the OSC stack.

The sliders , dunno , i did not test them out

You process ase normal. It came out a bit stronger then the OSC stack only...but was not that impressive , but as said i did not test further.

I want to redo this cause i have L-enhance stack of 3 hours whilest the former one was only 104 minuts...

Only unsure if it makes sense...besides only one experiment is not much is it?
jackbak
Posts: 3
Joined: Sun Jun 14, 2015 3:38 pm

Re: OSC Optolong l-eNhance colour

Post by jackbak »

Yeah nice results. As you say more work. I am pursuing automation so my time is spent processing not fat finger fiddling with equipment.
I also live only in the linux world so while I think Ekos can tell me about rotation I don't quite know how. Further to saving me time I would like
to automate StarTools processing to be identical from one set of shots to another (remember linux world).

Any way great results, Stefan.

Jack
fmeireso
Posts: 52
Joined: Mon Sep 28, 2020 8:46 pm

Re: OSC Optolong l-eNhance colour

Post by fmeireso »

So,

Use L-enhance stack of about 180 minuts as Luminance and a OSC stack of 150 minuts for R and G and B (Compose module)
Alignment of the two separate stacks via Siril.

Processed the stars for coloring separtly and by cutting the blue slider some color appeared in the stars. Still too many small bluish stars but some yellow and white stars also turned up ..

Dunno

HA red on the outside and the 'ugly' :D blue cyan for the OIII/Hb mix in the center...
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firebrand18
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Joined: Tue Feb 04, 2020 1:43 pm

Re: OSC Optolong l-eNhance colour

Post by firebrand18 »

Interesting suggestions from all, worth trying out to get the nasty blue/cyan gremlin pushed back a little (besides tweaking the RGB sliders in Color module).

In the Compose module, after putting L-Enhance data in Luminance and Visual Spectrum in RGB slots, what would you set the Luminance, Color setting to?
fmeireso
Posts: 52
Joined: Mon Sep 28, 2020 8:46 pm

Re: OSC Optolong l-eNhance colour

Post by fmeireso »

Guess the nasty blue cyan is a trademark of OIII.

Still don't understand why there are so much red Rossetas , seems just not very accurate.. :?
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Re: OSC Optolong l-eNhance colour

Post by admin »

fmeireso wrote: Thu Mar 04, 2021 11:14 pm Guess the nasty blue cyan is a trademark of OIII.
If you don't want different coloring, then maybe you should not be recording in multiple bands? You can make mono images as well from your data ("L + Synthetic L from R(2xG)B, Mono" for and OSC or DSLR) and give the resulting image a false color.
The whole point of recoding multiple bands and channels, however, is to make different features of equal brightness still distinguishable by their color.
Still don't understand why there are so much red Rossetas , seems just not very accurate.. :?
"Don't believe everything you see on the Internet" :lol:

A fully red Rosetta is indeed not accurate if that rendition is supposed to be a visual spectrum rendition (all HII areas are pink/purple), the same thing goes for a white M42 core or a white M31. Have a read of the Balmetr series Wikipedia article I linked to before to learn more about what causes the emissions (for hydrogen). From there, you can understand better which emissions you are actually recording and what color they are.

Coloring is probably one of the most misunderstood subjects in AP. :(
Ivo Jager
StarTools creator and astronomy enthusiast
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