Nocturna (1979)

The horror comedy Nocturna: Granddaughter of Dracula (1979) was the first film to introduce audiences to the notion of a Hotel Transylvania, which is the tourist trap that Dracula's castle has been turned into after a tax lien is placed on the property. The title character, played by Nai Bonet, is the hotel's manager who falls for Jimmy (Antony Hamilton), a member of a disco group hired to play a show at the hotel. Accompanying him to New York City, Nocturna soon decides that she wants to leave the vampire life behind and live in the city that never sleeps as a disco queen instead! All of this is true. It's also true that we get nice look at Antony Hamilton's bare ass during a sex scene with the title character! That should give you a Nocturna emission!