This article discusses Nikon D850 DSLR White Balance tests I did in October 2020 at Cassiopeia Observatory. Using a standard white balance value makes it easy to adjust the sky background in the final image during post-processing. I had begun to wonder if my sky color temperature had changed over the years. Why would my sky color temperature have changed? Three likely causes: (1) the increase in LED lighting (usually at the bad color temperature of 5000K), (2) particulates in the sky from all the wildfires over the past few years, and (3) a decrease in precipitation to "wash" the atmosphere. I took several sky photographs and prime focus images at various color temperatures to see what I liked best and to establish a baseline to use in future years for comparison.

I set up the D850 DSLR with a 24-70mm lens on the observatory patio.

I did untracked f/2.8, 30 seconds, FL 24mm, exposures at various White Balance settings. These are the resulting images with the WB noted.

For sky photography I will generally use a White Balance of 4000K.

I used M27 (Dumbbell Nebula) as a test Deep Sky Object (DSO) for the D850 DSLR prime focus tests.

These are 5 minutes, ISO 4000, exposures at various White Balance values.

For prime focus imaging I will generally use White Balance 4000K.

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