"The ships are orbiting Earth's moon."
Translation:tera' maS lubavtaH Dujmey.
Luna is just the Latin word meaning moon.
It's also said that only people not from the Moon call it Luna. (Deep Space Nine, "Valiant")
Maybe Kronos has more than one moon, so naturally you wouldn't say Kronos's moon. Or maybe people used to say that until it blew up. How do you know Klingons don't say Kronos's moon or just the moon?
This sentence is suitably specific.