It's amazing how these calculations work out sometimes. When I was writing my Weinbaum RPG I wanted to know the brightness of the sun on Pluto, since Weinbaum described it as being like a moonlit night. Except that the maths really didn't support that, and I ended having to hand-wave it away:

Pluto's daylight actually ranges from two hundred to six hundred times brighter than moonlight on Earth, comparable to a badly overcast day on Earth or the lighting in an average home. It generally appears to be much darker because the Sun is perceived as a bright star, there is no atmospheric scattering of light, shadows are completely dark, and most of the surface materials absorb light with minimal reflections.