One of six calotype prints, showing a 20-inch reflecting telescope with speculum mirror [Nasmyth focus] on a modified altazimuth mounting [see 1933-21] built by James Nasmyth at his Patricroft works, Manchester. Taken by him at of his large house, 'Hammerhurst' near Penshurst in Kent and dated 29th May 1866.

Photograph (calotype print) taken in 1866 by James Nasmyth (1808-1890) showing his 20-inch reflecting telescope. A successful industrialist and engineer, Nasmyth used this telescope to made extensive observations of the Moon. Working from his drawings, he calculated the height of the lunar features by measuring the length of their shadows. These were then photographed with suitable lighting to produce better results than could be achieved at the time with direct lunar photography. Nasmyth went onto photograph a whole series of his lunar models. They were used to illustrate the book, 'The Moon' that Nasmyth published in 1871 with James Carpenter.