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Best way to combine RGB and dual narrowband data

Optolong L-eNhance Processing Duo-Narrowband Deep Sky Emission Nebula
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Daniele Borsari avatar
Daniele Borsari avatar
Hi,

I've been shooting the California Nebula for a week and managed to capture 15 hours with the Samyang 135mm, ZWO ASI533MC Pro and Optolong L-eNhance.

I think I'll do another 1 or 2 nights to reach 25 hour-ish integration and I also think I'll shoot RGB with just a UV/IR Cut not only for the stars, but also for the background nebulosity in Taurus.

What is the best way to combine UV/IR Cut and dual narrowband data in PixInsight including both Ha, Oiii and RGB?

Daniele
Engaging
Markus A. R. Langlotz avatar
Markus A. R. Langlotz avatar
Hello,

you should split  the Narrowband images inmto the 3 chaneels R,G and B, process R as Ha and (R+B)/2 as OIII.
OIII and Ha should be given the physically correct colors, as I describe here:
http://jupiter.n-t-l.de/knowledge_narrowband.htm

Into that image, you can blend in the stars from the RGB (VIS) image. An example of the cirrs nebula, I posted here lately:

https://www.astrobin.com/uzsxlb/

CS

Markus
Christoph Nieswand avatar
Christoph Nieswand avatar
Hi
If you prefer using scripts: try the NBRGBCombination Script.
The script allows to blend  R, G and B from a narrowband image into an RGB image.
I did it on fully processed NB and RGB starless images and it gave me almost the same result as blending the images in Photoshop using the lighter color mode.
The stars from the RGB are added in the end as usual.
Did not play with it very much, but maybe its worth to give it a try.

Chris
Helpful
HR_Maurer avatar
HR_Maurer avatar
Here's how i do it:
After preprocessing, in linear state, i separate the stars from the RGB image, and from the NB mono images. Then i produce NB color images using pixelmath, like
Ha: R = Ha, G = 0.001, B = 0.15*Ha
OIII: similar, but ~0.6*G, 1*B
then i do a background neutralization step, and add the NB color images. The last step would be blending the RGB stars back in.

Bringing structures from RGB in which arent present in NB requires some fiddling around, especially if you run into chrominance issues.
andrea tasselli avatar
andrea tasselli avatar
Add them up. And then blend the RGB stars back in. Don't forget to apply LinearFit before adding the two masters up.