how to alter colour balance of just nebulosity

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Forum_2017
Posts: 276
Joined: 10 Dec 2018, 16:23

how to alter colour balance of just nebulosity

Post by Forum_2017 »

Hi AA fans!
i've recently started using AA6 and learning. I have captured California Neb through full spectrum modded canon 1200d using a CLS CCD filter which has a greenish cast. I preprocessed using AA6 and png is at https://we.tl/KXRHwTnFtv

Was wondering whats the best way to use AA6 to change colour balance of just the nebulosity?

Many thanks, Les

Forum_2017
Posts: 276
Joined: 10 Dec 2018, 16:23

Re: how to alter colour balance of just nebulosity

Post by Forum_2017 »

Hi, the image was saved "stretched" so it's hard to find out the problem. It cannot be processed further. It would be very useful to see the FITS right after Preprocessing, without any processing, or (much better) an original CR2.

It seems to me that all colours are "off", maybe something went wrong with debayering?

By the way, after Preprocessing the first recommended command is Color Curves. But again, it's hard to tell without the original image.

Forum_2017
Posts: 276
Joined: 10 Dec 2018, 16:23

Re: how to alter colour balance of just nebulosity

Post by Forum_2017 »

Hi Fabio sorry -see here for an unstretched version plus a few original FITS (converted from CR by SGP) https://we.tl/CTxFFzwvnk
thanks, Les

Forum_2017
Posts: 276
Joined: 10 Dec 2018, 16:23

Re: how to alter colour balance of just nebulosity

Post by Forum_2017 »

i played with demosaic and got a better result

Forum_2017
Posts: 276
Joined: 10 Dec 2018, 16:23

Re: how to alter colour balance of just nebulosity

Post by Forum_2017 »

Yes, the FITS files is flipped so the correct pattern is the lower-left (this could be found opening a single image into AA then RGB demosaic). Considering that there is no dark frame, leaving the hotpixel correction to 30-40% seems better to me. I also left Saturation to 30-40%.
After the Preprocessing and some minor filtering here are two possible results:

Forum_2017
Posts: 276
Joined: 10 Dec 2018, 16:23

Re: how to alter colour balance of just nebulosity

Post by Forum_2017 »

A trick that could be used on similar images is: after the final result is obtained, try the command Color / Split RGB, and take a look at the R,G,B frames. Often the R image contains a detailed image of the nebula that can be used for increasing its contrast, using LRGB, e.g.

1) Make a copy (F2) of the final result.
2) LRGB the copy with the R frame.
3) Menu Arithemic / Average to mix the copy with the original result.

Forum_2017
Posts: 276
Joined: 10 Dec 2018, 16:23

Re: how to alter colour balance of just nebulosity

Post by Forum_2017 »

many thanks Fabio.
interesting that AA6 for some reason didn't detect the most appropriate debayer setting when using preprocessing tools but did when opening one image and using demosiac from colour menu - unless I altered the settings by mistake.

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