What should be the WB_R and WB_B settings for ASI2600MC Pro camera ?

jcj2249

I'm using a ASI2600MC Pro using KStars/Ekos on a Mac.
The default settings of the camera are : WB_R = 52 and WB_B = 95.
These settings seem a bit weird to me .
Should not they be : WB_R = 50 and WB_B = 50 ?
![

zwo-ccd-asi2600mc-pro-controls.pdf

1MB

](https://)

w7ay

jcj2249 Should not they be : WB_R = 50 and WB_B = 50 ?

Nope.

In case it is what you are thinking, WB is to adjust the post-Bayer values, not to compensate for Bayer. I.e., WB is applied to an image that has already been previously deBayered to a native RGB image before white balancing.

The white balance factors are there to adjust for sensor efficiencies of the red and blue parts of the spectrum. The blue part of most sensors are typically deficient, and usually need a lot of boost.

If you want a daylight color balance, for example, just point the camera at a Kodak gray card under noonday Sun. Then adjust the "WB" values so that the red, green and blue historgrams line up moderately well. Most people don't bother, and they just wing it by adjusting the historgrams so that the light from a planet itself is white balanced.

https://www.kodak.com/en/motion/page/gray-cards

By the way, if you are OCD (or do photography seriously) and get a gray card, make sure you store a Kodak gray card under wraps when not in use, otherwise it will change "grayness" over time. Mine is well over 20 years old now, and still usable.

Chen

jcj2249

Thanks Chen. Thus I'll leave the settings as their default WB_R = 52 and WB_B = 95.

enaiman

jcj2249 Adjust the settings until you don't see any colour cast (the night sky should be grey, not yellow, blue,red or green).

w7ay

enaiman the night sky should be grey, not yellow, blue,red or green

Also, nope.

Believe it or not, night sky is actually blue. Exactly the same Rayleigh Scattering works at night (of course) as it does in the daytime to create the blue shift.

https://en.wikipedia.org/wiki/Rayleigh_scattering

Quote from the wiki: "In locations with little light pollution, the moonlit night sky is also blue, because moonlight is reflected sunlight,..."

Here is a real-world example of the night sky when I had white clouds, and used the clouds as reference for my white point. It is an image from my all-sky camera (you can actually see a couple of stars through the poor sky transparency) in the middle of the night (10:05pm), and with camera gain tweeked way up (causing the noisy image). Notice clouds are white and sky is blue.

Had I set the white point so that the sky is a neutral gray, the clouds would have then become yellow.

Chen

enaiman

w7ay Potato-potato Chen
You are right about a little bit of blue being present but if you are in a pitch dark area, I dare you to find that blue cast in the sky. What are you showing is a night sky with light pollution, possibly Moon light and FYI your clouds are yellow not grey 😛

Yes, the clouds are used for white balance.