Spencer, Browning & Rust Octant

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
Object Name
date made
ca 1800
Spencer Browning & Rust
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
place made
United Kingdom: England, London
ID Number
catalog number
accession number
Measuring & Mapping
See more items in
Medicine and Science: Physical Sciences
Data Source
National Museum of American History, Kenneth E. Behring Center
Credit Line
Mount St. Mary's College

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