Author Topic: Help for color balancing  (Read 1521 times)

Offline astroedo

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Help for color balancing
« on: 2013 September 10 12:38:58 »
 Hello to all forum users.

I have a problem in color balancing the linked picture of NGC 7000.
The picture is a composition of 31x120 seconds calibrated shots.

The frames was took with my modified Canon 350D and a quite old Leitz Elmarit-R 180mm F/2.8 lens set @ F/4.

The main problem is that the dim Milky Way starlets  that fill the image are very very green and i cannot get a decent color balancing of both nebula and stars on the background.

SCNR makes the image much better, but it does not solve the problem completely

As last resort I was thinking to create a starmask or a range mask and desaturate this stars, but probably someone more skilled could do something better.

Here the dropbox link
https://www.dropbox.com/s/y37wygepihilplh/ngc7000_31x2min_PI.fit


Off topic: Someone has an Idea about why this stars are so green?

Thank you

Edoardo

Offline Ignacio

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Re: Help for color balancing
« Reply #1 on: 2013 September 11 05:52:05 »
Hi Edoardo,

I looked at your image, and the problem is that you have very different FWHM values for each color channel (RGB): 2.5 pixels on G, 3.2 on B and over 5 on R. This translates into color halos/rings around bright stars, and greenish color for the tiny stars in the background, since the R and B channels are spread thin and the G prevails (only channel in actual focus).

You can try to correct this by first deconvolving the R and B channels independently, trying to end up with a FWHM of 2.5 pixels in both case. Then combine with the G channel, and then color balance the image.

good luck,
Ignacio

Offline astroedo

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Re: Help for color balancing
« Reply #2 on: 2013 September 11 07:40:14 »
Thank you for precious hint!
I will try and I'll let you know the result.

bye

Edoardo