Ertel & Sohn Universal Instrument

In 1841, after seeing the Ertel universal instrument at the Depot of Charts and Instruments (soon to become the U. S. Naval Observatory), Father James Curley determined to acquire a similar instrument for Georgetown College (now University), where he served as professor of mathematics and natural philosophy. Father Curley's quest for funds was successful, and within a few years he was using "an Universal or Altitude and Azimuth Instrument, reading to 10 seconds, by Ertel & Son, of Munich," to orient the walls and determine the position of the new Georgetown College Observatory, and to determine the positions of several prominent sites in Washington, D.C. This is the instrument that Curley acquired for Georgetown College. The horizontal and vertical circles are silvered, graduated to 10 minutes, and read by verniers and magnifiers to single seconds. A second telescope is below the horizontal circle. The signature reads "Ertel & Sohn in München" and "Utzschneider u. Fraunhofer in München."
Ertel & Sohn made the mechanical parts of the instrument. Traugott Leberect Ertel (1778–1858) had joined the Mathematical–Mechanical Workshop in Munich around 1812 and become its sole proprietor around 1820. It was probably he who designed this instrument. In 1834, when Georg Ertel (1813–1863) was taken into partnership, the firm began trading as Ertel & Sohn. They exhibited a larger but still portable universal instrument at the Crystal Palace Exhibition of 1851, and an "Instrument universel pour les observations astronomiques et terrestres" at the Paris Exhibition of 1855. The Utzschneider u. Fraunhofer signature refers to the Optical Institute that made the lenses for the instrument. Since Merz u. Mahler became proprietors of the Optical Instrument in 1840, the Georgetown instrument may have been one that had been in stock for some time.
Ref: Francis Heyden, "Astronomy at Georgetown College," Records of the Columbia Historical Society 53–56 (1953): 155–172.
Annals of the Georgetown Observatory, vol. 1 (1852), p. 14.
Exhibition of the Works of Industry of All Nations, 1851, Reports by the Juries (London, 1852), pp. 250–251.
Currently not on view
Object Name
universal instrument
Ertel & Sohn
overall: 18 in; 45.72 cm
horizontal circle: 11 in; 27.94 cm
vertical circles: 6 1/2 in; 16.51 cm
lower telescope: 17 in; 43.18 cm
place made
Deutschland: Bayern, Munich
ID Number
catalog number
accession number
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Medicine and Science: Physical Sciences
Measuring & Mapping
Surveying and Geodesy
Data Source
National Museum of American History, Kenneth E. Behring Center


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