OSC Optolong l-eNhance colour

[firebrand18]

Team, following this thread with interest. I also use the L-Enhance filter extensively for emission nebulae with my QHY168C OSC, WO GT-81 APO and StarTools for all processing.

I follow the Compose process by loading the same dataset FITS stack in the R, G, B slots and select L + Synth L From R(2xG)B, R(GB)(GB) (Bi-Color from OSC/DSLR) option.

Once in the color module and choosing Bi-Color preset, I get the expected Ha for the object and Cyan for stars/background. I tweak sliders to adjust color balance but wondering how you get this result on the Rosette and others like it with distinct red outer area and Cyan middle area; switching to a different composite in the Matrix menu always yields a uniform color.

Is all data captured with the L-Enhance and no other filter? How do you get the 2-tone I see here?

I'm working on IC1396 (Elephant Trunk) with 10 hours total integration and get nice Ha (red) result but no 2-tone.

Maybe I'm not understanding how this works.

I do get the red and cyan right off the bat with the Veil nebula complex but not objects like Wizard, Heart, Soul, etc.

Thanks for any advise and process flow.

Cheers,

Nick

[admin]

I tweak sliders to adjust color balance but wondering how you get this result on the Rosette and others like it with distinct red outer area and Cyan middle area; switching to a different composite in the Matrix menu always yields a uniform color.

The mappings of R:G:B to the other bands (for example Ha and O-III) you recorded dictate the behavior of the red/green/blue bias sliders.
If mapped R:G:B to H:O:O, the red bias slider should perfectly boost the red (Ha), while either the green or blue bias sliders should perfectly boost the cyan (O-III). If the signal is there, you should always be able to bring it out and define/throttle its dominance (in terms of coloring).

I do get the red and cyan right off the bat with the Veil nebula complex but not objects like Wizard, Heart, Soul, etc.

Boosting/balancing the two bands is almost always needed, for multiple reasons. One reason is that the default color balancing routine in StarTools uses star color for balancing. When recording narrowband Ha/O-III, these star colors are typically heavily skewed to blue, which makes the algorithm over-compensate and boost the red (stars are usually very blue in HOO bi-color composites; you can tone them done selectively if that is objectionable). The other reason is that Ha emissions are by far the strongest emissions vs O-III when recording the same exposure time. Furthermore, some objects may not have much in the way of O-III emissions at all; it is important to distinguish a narrower band filter such as the L-eNhance from a pure narrowband filter. A duo/tri/quadband filter often also records some blue star light as well as H-beta (which correlates with H-alpha). This has huge implications for the blue/cyan in objects that are poor in O-III emissions; it means that they will readily show blue/cyan when recorded with a duo/tri/quadband filter, but not when recorded with a much more narrow/strict O-III filter.

Thanks for any advise and process flow.

If you do everything according to best practices (it sounds like you do) and any blue/cyan coloring will not show up despite boosting the green or blue channels, then it may simply mean there is little to be had. In that case, I urge you to resist the temptation to resort to non-kosher manipulations (that is, if you wish to present your image as a documentary photograph to your peers). Such non-kosher manipulations are a little outside the scope of this thread, but a common one is to manipulate the two emission datasets individually (stretching, sharpening, etc.) and only then combining them into a composite; please don't do that!

[firebrand18]

Thanks Ivo; makes sense and appreciate the response; 100% agree with you as I follow the mantra of not changing things to looks "non-kosher"; I am all about keeping what I capture natural and scientific.

Shooting from a Bortle 8 location doesn't exactly makes things easy capturing subtle details and colors!

I'm relatively new to astro imaging and processing; here is what I came up with on IC1396 so any constructive criticism is welcome. Love StarTools!

https://www.astrobin.com/full/xo3duu/B/

Cheers!

[fmeireso]

So i worked on the Rosetta..

congrats for the result! I also tried this object last week, with the same filter, but I like more your processing than mine:
NewComposite3_signed.jpg

I like your stars more though.

Quite challenging to process stacks witht the L-enhance... The filter sure brings alot or more detail in ,but colorwise it is a bit challenging. The blue/cyan is something , dunno, weird....to me. After all cyan is a kind of greenish blue..
I like a red Rosetta better ,but then again ones misses the OIII in it, well i guess..

[Stefan B]

Quite challenging to process stacks witht the L-enhance... The filter sure brings alot or more detail in ,but colorwise it is a bit challenging. The blue/cyan is something , dunno, weird....to me. After all cyan is a kind of greenish blue..
I like a red Rosetta better ,but then again ones misses the OIII in it, well i guess..

If it's only the stars' color which you dislike you could set a star mask selecting only the stars. The automatic star masks in 1.7 are pretty good. In the color module you can now desaturate the stars to your liking. They will appear white instead of cyan if you completely desaturate them. Or you could change the color balance to yellow or whatever. But they will remain rather uniform and not natural. The price of narrowband I guess.

All the best
Stefan

[fmeireso]

Yes , i understand the stars color is ruined so i try to get them white...so be it .

But the blue Cyan from OIII is ...well , you know...maybe less appealing....

I still wonder is blue/cyan really the color of OIII ?

As far as the filter itself , well it is quite stunning , considering the big amount of nebulae then gets in opposed to no filter with an unmodded cam...

[fmeireso]

Another bi-color approach. Skipped the blue cyan a bit.
Detail is quite amazing for almost 3 hr with a unmodded DSLR. Stars put to desturated white.
Personaly i don't find the pinkish red appealing...

Thoughts?

[admin]

But the blue Cyan from OIII is ...well , you know...maybe less appealing....
I still wonder is blue/cyan really the color of OIII ?

A teal green is indeed what O-III looks like to the human eye. Some people can actually see this color with the naked eye in the core of M42.
H-beta is a sort of aqua blue.
Mix the two and you get cyan (roughly).

(from https://www.testar.com.au/products/opto ... nce-filter)

It is furthermore a convenient color rendering, as the two colors are at almost opposite parts of the spectrum, making it easy for humans to discern.

Given that Ha tends to coincide with other Balmer lines (Hb being the most prominent after Ha); Red (Ha) + Acqua (Hb) yields a pink/purple. In the visual spectrum you can add the other Balmer series as well which are all blue to arrive at a slightly more fluorescent pink/purple. This specific color you probably have seen in many visual spectrum StarTools renditions.

[Stefan B]

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.

Some people can actually see this color with the naked eye in the core of M42.

Well, not with the naked eye but with the help of an 8 inch dob. Saw that yesterday. I have to admit I still don't favour this color in images

Best
Stefan

[fmeireso]

This does work. But the result is not so strong..

I should perhaps try again, because know i have a stack of almost 3 hrs with the L-enhance.
The first try i had only 104 minuts.

First i will have to get them registered off course..that worked the other time with Siril, guess i can do it again...