What is the best White Balance setting for astrophotography?
This question gets asked surprisingly often. I call this surprising because the answer should always be: it doesn’t matter!
This may seem counter intuitive as we all experience the influence of WB on the color of the image. Furthermore we see people mentioning the WB they used for pictures in the details of many astrophotos so surely it must matter?
No. It really doesn’t as long as you are shooting in RAW, which you should be doing anyway for astrophotography!
The RAW format basically contains the image data that is not being processed* in the camera. It is often called the ‘digital negative’ and compared to the negatives from the film age as it is serving a similar purpose; it stores the image data unprocessed.
Therefor you always need to ‘develop’ a RAW file!
The camera settings that were applicable for the exposure are stored (separately!) in the metadata of the file. Most programs and previewers will use this metadata for the initial preview of the image.
RAW format and White Balance
And this is where a lot of the confusion comes in; Most programs and previews will show a RAW just fine, based on the actual camera settings used. Therefor they will show a ‘real’ difference depending on these settings and thus it is perceived as if it matters what settings were used. Makes sense right?
But no, it doesn’t matter as these settings come from the metadata and can easily be changed! It didn’t and doesn’t affect the ‘real’ image data of the RAW file!
If you open and use RAW files in PixInsight for instance, all this metadata with camera settings is simply ignored and you work with the real RAW data. Please make sure you have the right DSLR_RAW settings applied in PixInsight.
As for the white balance; this is just part of the metadata. Therefor it can easily be changed in post processing if you would want to, and moreover; it is ignored in the astro post processing workflow.
So if anyone still wonders what the best white balance is for astrophotography, the answer is real simple; it doesn’t matter because it doesn’t affect the RAW image data.
Update: It seems quite some people are actually using a form of Custom WhiteBalance to achieve correct colors in their astrophotos. I would strongly advice not to do this as applying in camera WB setting will affect the data you are working with with risks (according to some; guarantees) of hurting your data. There are better ways for proper color calibration!