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 states that it is based on a hugely popular book by the astronomer and well-known lecturer, Robert Ball (1840-1913). It consists of a circular plate with a celestial map which revolves by means of a rack and pinion movement in a flat, painted metal case with an oval cutaway exposing the visible part of the sky at the latitude of London, N 51.5 degrees. At the top of the metal box is a label pasted on that gives instructions for use.