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Octant

Octant

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Description
An octant measures angles by bringing two images together—that of the sun, for instance, and the horizon—and was used primarily to determine latitude at sea. The form was described by John Hadley in London in 1731 and still in use in the early twentieth century.
This example was made during the American Revolution, and there are faint markings on the scale that may read "equality" and "justice." It has a mahogany frame and index arm, and ivory inset. The boxwood scale is graduated every 20 minutes from -5° to +95° and read by ivory vernier to single minutes of arc. There is also a back sight and a back horizon mirror for measuring angles greater than 90°. The radius is 17.75 inches. The "B. CONDY PHILADELPHIA 1778" inscription refers to the American instrument maker, Benjamin Condy (d. 1798).
Location
Currently not on view
Object Name
Octant
Date made
1778
business owner
Condy, Benjamin
maker
Condy, Benjamin
Place Made
United States: Pennsylvania, Philadelphia
Physical Description
wood (overall material)
brass (overall material)
glass (overall material)
Measurements
average spatial: 7.9 cm x 42.1 cm x 51.8 cm; 3 1/8 in x 16 9/16 in x 20 3/8 in
overall: 4 1/2 in x 22 in x 19 1/2 in; 11.43 cm x 55.88 cm x 49.53 cm
ID Number
1992.0312.01
catalog number
1992.0312.01
accession number
1992.0312
See more items in
Medicine and Science: Physical Sciences
Measuring & Mapping
Data Source
National Museum of American History
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