This is one of a series of drawings done by Sir John Frederick William Herschel in 1840 when he had his father's 40ft reflector telescope dismantled fearing the severely rotten frame might collapse.

John had just returned from South Africa where he had been cataloguing all the nebulae, double stars and star clusters visible through his 20ft telescope in the southern hemisphere with his young family in tow. It was in part for the safety of his young children that he had the telescope dismantled.

The 40ft had for a time been the largest telescope in the world and attracted visitors from around the world to Slough, it even features as a landmark in some Ordnance Survey maps of the time and so to mark this end of an era John and his family conducted a small ceremony.

This drawing was done using a camera lucida. The drawing is in pencil, the title is written at the top and bottom in pen and sepia ink. The full title reads: 'J. F. W. Herschel declin Cam. Luc. April 5, 1840. Slough. The 40ft reflector with all the woodwork down. No. 536. Vol. 3. fol. 71'