Pocket planetarium, 1935-1939

Hoepli's pocket planetarium or star identifier date, c. 1936

Dated to 1935--1939, this pocket planetarium was devised by Ulrico Hoepli in Milan, Italy. The device consists of a hinged book of circular paper and card star maps with a storage case. Like a conventional planisphere, the gadget is designed to show the appearance of the heaven at any time during the year. In addition, the Hoepli planetarium can be used to show the sky from any part of the Earth. In operation, the user opens the star charts at the relevant map and then places the whole set in the open storage case. The chart is then rotated to the relevant latitude of the user, so that scales on both map and case correspond.