[Aavso-photometry] Light box question]

[Ben Davies]

While on the subject of flats:

I was talking to an astronomy professor recently who told me that when 
doing astronomy on the big telescopes, he made his flats from the night 
sky surrounding the object he was looking at.  I tried to press him on 
how that could possibly work, but his English was not so good and I had 
trouble understanding exactly what he was saying.

I assume it is doable, because he was insistent on the point.  Does 
anyone know anything about this?

Ben Davies