Cassegrain reflecting telescope, 1762-1774

Made:
1762-1774 in London
maker:
Jesse Ramsden

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Science Museum Group Collection
© The Board of Trustees of the Science Museum

Science Museum Group Collection
© The Board of Trustees of the Science Museum

Cassegrain reflecting telescope of 6 inch aperture by Jesse Ramsden, London on an adjustable equatorial mounting with 2 spirit levels and 3 levelling screws. Accessories include, a filar micrometer, 3 small speculum mirrors, 3 eyepieces [1 by Nairne & Blunt], 2 adjustor keys and a finder telescope.

Dated to 1762--74, this reflecting telescope uses the Cassigrain optical configuration. Made by Jesse Ramsden then the foremost instrument maker in London, it has a 6-inch metal mirror. The telescope is mounted on an improved version of James Short's so-called 'universal', a portable equatorial stand with a brass fork holding the tube and an adjustable polar axis. As it is used on a table or similar surface, the portable telescope has three levelling screws and a pair of sprit levels. Such a lavish instrument would have only been affordable to a rich aristocratic dilettante.

Details

Category:
Astronomy
Object Number:
1913-281
type:
telescope - reflecting
taxonomy:
  • furnishing and equipment
  • measuring device - instrument
  • micrometer - angle
  • furnishing and equipment
  • tools & equipment
  • optical instrument
  • telescope
  • telescope - reflecting
  • furnishing and equipment
  • tools & equipment
  • optical instrument
  • telescope
  • disciplines
  • disciplines
  • science
  • natural sciences
  • physical sciences
credit:
Mr Thomas H. Court