Dollond Refracting Telescope with Divided Glass Micrometer

Description
This brass telescope has an achromatic objective of 2.75 inches aperture, a finder, several eyepieces, two telescoping braces, two control rods, a split objective micrometer, a brass equatorial mount, and a wooden tripod. The tube is 43.5 inches long. The faceplate at the eye end is marked “DOLLOND * LONDON.” For storage, the telescope fits into a mahogany box with a hinged lid.
This seems to be an example of the brass telescope “of 3½ feet focal length, with an aperture of 2¾ inches, two eye tubes for Land Objects, and two tubes for Astronomical purposes” that George Dollond was offering in the 1830s. That instrument could be had with either a brass stand for use on a table, or “a mahogany folding stand, to be used on the Floor.” It could, moreover, be “supported in the centre of Gravity, and applied to a socket that may be turned to any latitude, so that the Telescope may have an Equatorial Motion” The complete outfit cost £50. The micrometer would be extra.
The Dollond family began working as opticians in London in 1750, and gained fame in 1758 when John Dollond introduced his design for achromatic lenses. John Dollond was also responsible for the split objective micrometer.
Ref: “A Description of a Contrivance for Measuring Small Angles, by Mr. John Dollond; Communicated by Mr. J. Short, F.R.S.,” Philosophical Transactions of the Royal Society of London 48 (1753): 178-181.
“An Explanation of an Instrument for measuring small Angles, the first Account of which was read before the Royal Society May 10, 1753. By Mr. John Dollond,” Philosophical Transactions of the Royal Society of London 48 (1754): 551-564.
George Dollond, A Catalogue of Optical, Mathematical, Philosophical Instruments (London, ca. 1830).
Gloria Clifton, “Dollond Family,” in Oxford Dictionary of National Biography.
Location
Currently not on view
Object Name
telescope, refractor
date made
probably 1760s
maker
Dollond
Physical Description
brass (overall material)
wood (overall material)
Measurements
overall: 13.5 cm x 23 cm x 116 cm; 5 5/16 in x 9 1/16 in x 45 21/32 in
place made
United Kingdom: England, London
ID Number
1979.1110.01
accession number
1979.1110
catalog number
79.1110.1
subject
Astronomy
Science & Mathematics
See more items in
Medicine and Science: Physical Sciences
Data Source
National Museum of American History, Kenneth E. Behring Center
Additional Media

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