A 9 inch Newtonian primary mirror of a metal thought to be speculum.

In a Newtonian reflector telescope the eyepiece is at the side of the tube. Light comes in at one end, is reflected off the objective (or primary) mirror and onto this mirror which directs the light towards the eyepiece. If one of those made by Sir William Herschel in the late 18th - early 19th century this would have been used with one of Herschel's 10ft telescopes which he made both for himself and for sale.

The mirror has a circular metallic lid, and both mirror and lid are in a square wooden box packed into the box with pieces of cork. The box lid is screwed into place (one screw is missing). There is a metal handle on the lid of the box. Written in ink on a paper label on the lid of the box it reads

'9-inch metal mirror. ? Herschel'. Also on the lid, in white chalk is written '[24] F'.

However this does not relate to the numbering system used by Steavenson to catalogue the Herschel collection based in the family home in Slough in 1924 as Steavenson's F24 is an iron ring holder for a polisher.

This mirror belonged to the Royal Astronomical Society until 1984 when it was purchased by the Museum. The Royal Astronomical Society were never convinced as to its provenance. Its link to the Herschel family is questionable and based purely on the size and material of this mirror which is typical of those made by Sir William Herschel.