> If the "DC value of the sky" could be removed with a simple high pass filter, then there would be no need of doing anything else. The positions of the stars in the sky would be known, and techniques like the one in the article would apply.

This doesn't make any sense. Even if one could estimate ground truth DC, removing it would leave noise at every other frequency bin.

But this is beside the point. Your questioning isn't coming from a place of curiosity.

I direct you to the HN guidelines: "Be kind. Don't be snarky. Have curious conversation; don't cross-examine."