Helen Hed

“And give me some coffee. Black as midnight on a moonless night."
Harga looked surprised. That wasn't like Vimes.
"How black's that, then?" he said.
"Oh, pretty damn black, I should think."
"Not necessarily."
"What?"
"You get more stars on a moonless night. Stands to reason. They show up more. It can be quite bright on a moonless night."
Vimes sighed.
"An overcast moonless night?" he said.
Harga looked carefully at his coffee pot.
"Cumulus or cirro-nimbus?"
"I'm sorry? What did you say?"
"You get city lights reflected off cumulus, because it's low lying, see. Mind you, you can get high-altitude scatter off the ice crystals in--"
"A moonless night," said Vimes, in a hollow voice, "that is as black as coffee.”
― Terry Pratchett Pratchett, Men at Arms