Not entirely sure whether this belongs here or in “Atmospheric Phenomena”. Sky brightness is predominantly confined to the atmosphere but a component also comes from dust in solar orbit.
The paper https://www.sciencedirect.com/science/article/pii/S0022407319309653 came to my attention today. It describes how standard commercial DSLR cameras can be used for rigorous multi-band photometry of the sky background glow.
I’ve not yet had the time to grok it fully but I am already impressed.