Ramsden Refracting Telescope

A telescope on an equatorial mount allows an astronomer to follow a star as it moves across the sky (or, rather, as the earth rotates below it). Several British and European forms were introduced in the latter decades of the 18th century. This is an example of the Universal Equatorial telescope designed and made by Jesse Ramsden.
Ramsden’s Universal Equatorial instruments were expensive, and appreciated by wealthy men. We do not know who first owned this example. But we do know that Thomas Jefferson had an instrument of this sort.
The telescope is 16.25 inches long. The achromatic objective has an aperture of 2.5 inches. The eyepiece is missing. There is a graduated circle for right ascension and another for declination, as well as a mechanism for adjusting the instrument for use at any latitude. The horizontal limb is marked “Ramsden London.” Gift of the Perkin-Elmer Corporation.
Ref: Description of a New Universal Equatoreal, Made by Mr. J. Ramsden, with the Method of Adjusting in for Observation (London, 1773).
Description of the Universal Equatoreal, and of the New Refraction Apparatus, Much Improved by Mr. Ramsden (London, 1791).
Anita McConnell, Jesse Ramsden(1735-1800). London’s Leading Scientific Instrument Maker (Aldershot, 2007).
Allan Chapman, “Jesse Ramsden” in Oxford Dictionary of National Biography.
Currently not on view
Ramsden, Jesse
place made
United Kingdom: England, London
Physical Description
brass (overall material)
overall: 29 in x 15 3/4 in x 15 1/2 in; 73.66 cm x 40.005 cm x 39.37 cm
ID Number
accession number
catalog number
Credit Line
Perkin Elmer Corporation
See more items in
Medicine and Science: Physical Sciences
Science & Mathematics
Data Source
National Museum of American History, Kenneth E. Behring Center


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