vdb142 - narrowband - have a try

[Herbert_W]

Hello!

I did vdb142 with narrowband (ha 2.5h, oiii 3h, sii 5h) and it is not
possible to me, to create a pretty colorimage with the hubble palette (s-h-o).
Usually the have a light yellow and blue - but my tries ends with flat colors without blue and yellow.

On the one side is the mixture of the channels with pixelmath important (there a a lot of recommendations in the forum),
otherside this can't be all - I suppose that curves, histo and saturation important as well - but I cant get it.

Maybe there is someone, who want to try my frames and show me his result.

The files are at: endor.pixinsight.org   Folder: HerbertWalter

or

vdb142 sii
vdb142 oiii
vdb142 ha

Thank you and best regards.

Herbert, Austria

[Lex]

Hy Herbert,

I have downloaded the files and will try to give it a try during the WE...
Will keep you in the loop..
Thanks

[Herbert_W]

Hi Lex!

Thanks - I'm very interested on your result!
Its not so easy to do it in PI - its a pity to miss a tool in PI to mix narrowband frames.

Best regards.
Herbert, Austria

[vicent_peris]

Hi Herbert,

I have a result, will show it on next week, be patient.


Regards,
Vicent.

[Raymond]

Hi Herbert
I've actually not a lot of experience in combining narrowband images, but I wanted to see what I could get with your data. So here is my result...
--------------------------------------------
 1. Star Alignment
 2. PixelMath   R: Ha
              G: SII
             B: OIII
 3. Dynamic Crop
 4. BN using a small Preview
 5. CC with structure detection
 6. Masked stretch  50 iterations
 7. HT  shadows:  0.042
      midtones: 0.260
 8a. Star Mask
   Scale: 5   Growth: 1
   Smoothn: 8
 8b. HT on Star Mask
   Shadows:  0.250
   midtones: 0.420
 8c. Invert Mask

 9. ATWT with Star Mask applied
   Bias: +0.010/+0.020/+0.025
         +0.020/+0.025/+0.030
        for layers: 3...8
 10. CT   RGB/K (S-curve; contrast)
   I: 0.11  O: 0.09
   I: 0.60  O: 0.76
--------------------------------------------
Is this a result similar to yours?

[Herbert_W]

Hi Raymond!

It looks great!! Thank you very much for processing.

Is this a result similar to yours?

If I use H-O-O for R-G-B, it looks similar to your result - nearly a "natural look" like RGB.

Very interesting is your workflow - thanks for the effort to list the detailed steps.
(although Star Alignment wouldn't have been necessary, because the frames are already aligned).

In the meantime I got 2 examples via PN. At the end I will show the results to compare
and discuss.

Thanks again and best regards.
Herbert, Austria

[Lex]

Hello Herbert;

This is the third time I try to process a NB image...

Here is what I've done:

01. Star Alignment
02. Dynamic Crop
03. Fast Rotation
04. PM: 0.8*SII + 0.2*Ha / 0.2*Ha + 0.8*OIII / OIII
05. Background Neutralization
06. Color Calibration
07. Masked Histogram ( Starmask inverted applied )
08. DBE
09. ACDNR
10. SCNR --> Green Average
11. Curves --> Lightness / Saturation

__________________________________________

That's it; my rendition of your Data

I hope you like it; I tried to apply HDRMT but as I am kind of short in time and still struggling with the different layer setting I satisfied myself with the end result.

[Herbert_W]

Hi Lex!

I hope you like it;

Yes, I like it - good looking colors!!
Thank you for processing and showing the result.
Very interesing are the factors to mix the channels " 0.8*SII + 0.2*Ha / 0.2*Ha + 0.8*OIII / OIII".

Did you guess your formula and hence it is a 'try and error game' or is it
a proven mixture?

At the moment I'm looking for a formula which takes the different signal strength into account.
But there is a lot to think about to measure the values, background, signal, bring it in relation, ...  and this takes time.
I'm not a mathematicien or physicist :-(

Thank you also for the detailed workflow ( staralignment would not have been necessary, its already done).

Best regards.
Herbert, Austria

[TeeJay]

Hello Herbert,

I also tried to process your Data in classical Hubble Palette. I hope you like the result. I used the Tone mapping Method from J-P Metsavainio, with a lot of modifications from me...

CS
TeeJay

[Lex]

Hi again,

You are welcome, in fact the channel mix factors came out of a tutorial that Juan has written.
I am no mathematics guy neither so I took the easy way, unfortunately, because i would like to have more time for trial and error what is not possible for the moment..

@TJ

I like your rendition very much; I think it is "closer" to the Hubble palette than mine. What are your Pixelmath channel factors if I may ask?

Thanks

[TeeJay]

Hi Lex,

actually i don't use any factors at all. My first step is to HistogrammTransform all the three images to the same level. To do so, I perform "Auto zero shadows" and check it with the 100x zoom, after that I set de Midtones to have the hill at 3/16... (I attached a screenshot for better understanding)
Those images don't have the high contrast of auto-SFT Images but this is not needed.
Then I use a CurvatureTransforamtion to set nearlly the same (visuall) contrast to all the images. (screenshot)
Now I finally map [SII] to red, H-alpha to green and [OIII] to Blue, without any factors.

I know this is not a scientific way, but it is very good for pretty pictures!

In the case I showed above, i do all this with Tonemapps (starless) and use a luminance ((lum from tonemapps) + Ha + OIII + SII) at the end...

CS
TeeJay

[Lex]

TeeJay,

indeed you use a very simple workflow. The only negative thing IMHO is that the star coloring is a bit towards red.
Have you neutralized the background and color calibrated your image?
This is really the only "negative" aspect of your rendering; again IMO

[TeeJay]

Lex,

yes the thing with the stars... Because there are no usefull color information from Stars in Narrowband images, I do a simple trick: Starmask -> CurvatureTransformation -> Saturation and C to zero.
That's it.
No BackgroundNeutralziation needed, because of the HistogrammTransformation to the same levels. But if you do to much CurvatureTransformation you will need it...

If I map narrowband images to "real color" with somethin like [R=(SII*2+HA)/2;G=OIII*0.5;B=(OIII+HA*0.333)/2], I use singel RGB exposures of the Stars to overlay.

CS
TeeJay

Edit: I reworked the Image, with better Star-removal and also did a real color version (unfortunatelly forgot the sharpening)...

[Lex]

Why doing it the difficult way if it is possible to do it easily 
Nice approach 
Thanks

[Herbert_W]

Hi TeeJay,

wonderful pictures and thanks a lot to process the frames and share your result and especially your method with the community!

Your completely different approach corresponds to my idea to create reproducible steps processing narrowband images.
I spend my time at the moment to retrace your steps and I have to say, it's not so easy.

Now I'm for one week on duty travel and will be back afterwards with my 'calculated' result -  my laptop with PI is in the package ;-)

Until then thanks to all for the contributions - maybe we will find a way to leave the 'try and error' method.

Best regards.

Herbert, Austria

@Vincent - I'm very curious to your result and method ;-)