Spencer, Browning & Rust Octant

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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 +99° 40' and read by vernier with tangent screw to single minutes of arc. There is also a back sight and a back horizon glass that can be used to measure angles greater than 90°. The "Spencer Browning & Rust London" and "SBR" inscriptions refer to a firm that was in business from 1784 to 1840. This instrument belonged to Mount St. Mary’s College in Emmitsburg, MD.The design suggest that it was made around 1800.
Currently not on view
date made
ca 1800
Spencer Browning & Rust
place made
United Kingdom: England, London
Physical Description
ebony (overall material)
brass (overall material)
ivory (overall material)
box: 12 cm x 43.2 cm x 37.5 cm; 4 23/32 in x 17 in x 14 3/4 in
octant radius: 13 3/4 in; 34.925 cm
overall in box: 4 3/4 in x 14 1/2 in x 16 5/8 in; 12.065 cm x 36.83 cm x 42.2275 cm
ID Number
catalog number
accession number
Credit Line
Mount St. Mary's College
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Medicine and Science: Physical Sciences
Measuring & Mapping
Data Source
National Museum of American History