I had a go at imaging Capella this afternoon in a clear, transparent sky after I’d finished with the Sun. I took 1000 frames with an exposure 879 us and gain set to minimum on an ASI1600 using a 90mm, f/6 refr and then took the same number of dark frames with the same exposure. Capella was quite close to the Sun so there is a lot of forward scatter from drifting pollen but, after calibration, and taking the V mag of Capella as 0.08 I get a sky brightness of 2.6 mag/arcsec^2. Remarkably close to what I expected. A video of the calibrated light frames is here:
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