40. Ocular micrometer by Dollond for the 8-foot refracting telescope
London, 1787
John Dollond Jr. (London ?-1804)
Peter Dollond (London 1730-1821)
brass
[Inv. MdS-42]

This moving wire micrometer, part of the accessories of the 8-foot refracting telescope with achromatic object lens purchased by the Specola in 1787 [file 37], was described in the 1843 inventory as follows:
"Ocular moving wire micrometer, which can take any angular inclination with external display that via an index shows the turns of the screw, which is used to move the wires. This micrometer has its own eyepiece lenses, and a colored glass with metal casing."

E. Baiada, A. Braccesi (1983), p. 123
R.C. Brooks (1991).
M. Daumas (1953).
G. LE. Turner (1981).