stars turn blue - darktable - white balance issue?

Software darktable
1

All;

I shoot a lot of milky way / stars. Often when I do a few simple edits such as:
white balance to cool white flourescent and then increase th exposure of the sky

I get lots of blue stars. Any thoughts on getting the stars back to white / mostly white?

See a example RAW & JPG (post darktable) attached. They are both released under creative commons
DSC_3124 DSC_3124.NEF (49.0 MB)
Thanks in advance

2

Looks like it’s your white balance choice:
“Cool white fluorescent” gives a temperature of ~3700K, which implies visible a shift towards blue compared to daylight WB. In addition, the green is lowered, causing a shift to magenta.

If I try your image, camera WB seems a lot better (a bit greenish). Or try using the spot setting and pick an area you want to be neutral gray. That should get you a decent starting point

3

Also, a lot of the stars are in reality blue. All of them are actually coloured, just or nocturnal vision is not good at detecting colour and makes them white.
You should try defringe. Most lenses show distortion for star photos and defringe helps a lot.

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4

Morning!

Just for fun, I ran your .NEF through the white balancing procedure outlined here:
https://discuss.pixls.us/t/call-me-stupid/19625

To my eyes, it made the image considerably cleaner.

Have fun!
Claes in Lund, Sweden

5

More than you probably ever wanted to know:

https://clarkvision.com/articles/color-of-stars/

Cut to the chase, the essential thing to take from that extensive missive, cut-n-pasted from the Conclusions at the bottom:

"The best way to show that color range is a daylight white balance on your digital camera. "

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6

@ggbutcher, you have a wealth of useful information.

7

My wife would contend the “useful” part… :smiley:

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