Ritchie Azimuth Circle

This circle was designed to fit atop a U.S. Navy Standard Compass.The inscriptions read "E. S. Ritchie & Sons, Inc. Brookline, Mass." and "2867" and "NEGUS, New York." The Ritchie ledgers, now held by Ritchie Navigation, indicate that it was made on April 10, 1941 and sold to T.S. & J.D. Negus, a New York firm that sold navigational instruments. The U.S. Naval Observatory transferred it to the Smithsonian in 1966.
This circle has two mechanisms for taking sights. In one, the rays of the sun are reflected from a cylindrical convex mirror to a right-angle prism on the opposite side of the ring, and then through a cylindrical lens below, appearing on the card as a bright bar of light. The other consists of sight vanes, hair line and reflector, for taking bearings of terrestrial objects.
E. S. Ritchie received his first patent (#49,157) for an azimuth circle in 1865, and another (#481,625) in 1892.
Ref: G. Dutton, Navigation and Nautical Astronomy (Annapolis, Md., 1948), pp. 33-34.
Currently not on view
Object Name
azimuth circle
date made
overall: 10 in; 25.4 cm
place made
United States: Massachusetts, Brookline
ID Number
catalog number
accession number
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Medicine and Science: Physical Sciences
Measuring & Mapping
Data Source
National Museum of American History, Kenneth E. Behring Center


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