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This octant has an ebony frame and flat brass index arm. The ivory scale is graduated every 20 minutes from -2° to +100° and read by vernier and tangent screw to single minutes of arc. There is also a back sight and back horizon glass used to measure angles greater than 90o. This instrument was probably made in England around 1800. The U.S. Navy transferred it to the Smithsonian in 1930.
Currently not on view
Object Name
radius: 12 in; 30.48 cm
overall: 14 1/2 in x 11 3/4 in x 2 5/8 in; 36.83 cm x 29.845 cm x 6.6675 cm
overall: 2 5/8 in x 11 3/4 in x 13 3/4 in; 6.6675 cm x 29.845 cm x 34.925 cm
ID Number
catalog number
Credit Line
U.S. Navy
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Medicine and Science: Physical Sciences
Measuring & Mapping
Data Source
National Museum of American History
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