Equatorial Sextant

Equatorial Sextant

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William Austin Burt submitted this model of his new equatorial sextant to the U.S. Patent Office in 1856. According to the published patent (#16,002), this instrument could be used to take azimuths, altitude, and time with one observation, and thus enable one to easily obtain the position and bearing of a ship at sea. This instrument was ingenious, but never found much of a market. Burt is better remembered for the solar compass that he introduced in the 1830s.
Ref: John S. Burt, They Left Their Mark. A Biography of William Austin Burt (Rancho Cordova, Ca., 1985), pp. 128-130.
Currently not on view
Object Name
equatorial sextant
Object Type
Patent Model
date made
Burt, William A.
overall: 11 7/8 in x 10 1/4 in x 5 5/8 in; 30.1625 cm x 26.035 cm x 14.2875 cm
overall: 12 in x 11 in x 5 in; 30.48 cm x 27.94 cm x 12.7 cm
ID Number
catalog number
accession number
patent number
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Medicine and Science: Physical Sciences
Measuring & Mapping
Science & Mathematics
Patent Models
Invention and the Patent Model
Data Source
National Museum of American History
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I have an item that appears similar to this but appears to be modern. Has anyone manufactured this for commercial sale? I cannot find any manufacturer's markings on my unit. Outer ring is calibrated for latitude, +/- 90 degrees and labeled CEL POLE in both directions. Second ring has scope mounts and also calibrated +/- 90 degrees. Second ring can also rotate on Z axis with ring marked E (+) LHA and W (-) LHA. Two down directed mirrors might be used to establish vertical. The entire device appears to be designed to rest on knife edges and rotate to maintain plumb. Would like to know if this is of interest or just odd. I've never seen a sextant like this that is not made to be hand held.

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