Planisphere by George Philip and Son, c. 1935
The planisphere (literally 'flat sphere') is the modern descendant of the astrolabe.
It compresses an entire hemisphere of stars into a small, hand-held map and can be adjusted to show the positions of the stars above your head for any date and time.
The device shows how the constellations cartwheel around the Pole Star (Polaris), bobbing above, then below, the horizon throughout the year.
Modern planispheres are manufactured from plastic but this early 20th-century example is made from card with elaborate gilt decoration. They are made for a specific latitude: this one is for 51.5 degrees north, suitable for London and Leipzig.