Planispheres are flat representations of the celestial sphere. By combining a star chart with a moveable window, they could reveal the constellations visible at a particular latitude on any night of the year. While the conception goes back at least to the 11th century and the name to the 17th century, it was in the 19th century that new and cheaper printing techniques meant that they could become readily available to lay audiences.

This planisphere is made of cardboard and paper, which is printed in colour lithography. It consists of a base plate, with a celestial map, and a horizon disc, moveable around the north pole. The horizon disc has an oval cutaway, exposing the visible part of the sky at the latitude of 51.5 degrees. A brass meridian is fixed to the horizontal disc and a mobile cardboard ruler is attached to the north pole. The various parts are held together with a brass rivet. Calendar, zodiacal and hour scales surround the whole, and compass directions surround the horizon cutaway.