This is one of nine wall hangings, all on astronomical themes, that were among many produced by the Working Men's Educational Union in the 1850s. They were printed lithographically on cotton, probably to avoid paper duty. The hangings would have been used in lectures, held at various locations, to illustrate the latest advances in knowledge. The Working Men's Educational Union (f. 1853) was a philanthropic society with the object of “the elevation of the working classes, as regards their physical, intellectual, moral, and religious condition”. Their chief means of achieving this was to encourage popular literary and scientific lectures “by preparing suitable Diagrams and other aids to lecturers” and to promote lending libraries and “mutual instruction classes”.

This example depicts diagrams of the optical principles of two types of reflecting telescope, the Newtonian and the Cassegrain.