I recently came across a reference for a “nocturnal for both bears.” It sounded, at first, like a piece of music written by Mussorgsky or perhaps Prokofiev, which it isn’t. It is a device used for telling time at night by the position of Polaris and the stars of the constellation Ursa Major, the “big bear.”
The instrument, known in English as a noctural and in French as a nocturlabe, is essentially an astroble to be used at night. As the pole star, Polaris, is in the constellation Ursa Minor, the “little bear” and the device involves sighting the stars from both big and little bears, the device is a “nocturnal for both bears.” It was first developed in the 1500s and was used up into the 18th century. As a device used for telling time at night, it was apparently only accurate to within 15 minutes or so.