Dip Circle

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This is one of eight dip circles that Edward Kahler made for the American expeditions sent to observe the transit of Venus across the face of the sun in 1874. It is marked "106." The vertical circle is graduated to 20 minutes. The horizontal circle is graduated to 30 minutes and read by vernier to single minutes. Both are silvered. The U.S. Naval Observatory transferred it to the Smithsonian in 1966.

Ref: Steve Dick, Sky and Ocean Joined (Cambridge, 2002), p. 250.

Currently not on view
Date made
ca 1874
Place Made
United States: District of Columbia, Washington
Physical Description
wood (overall material)
metal (overall material)
vertical circle: 6 in; 15.24 cm
horizontal circle: 4 1/2 in; 11.43 cm
overall in case: 11 1/8 in x 11 in x 11 3/16 in; 28.2575 cm x 27.94 cm x 28.41625 cm
ID Number
catalog number
accession number
Credit Line
U.S. Department of Defense, Dept. of the Navy, U.S. Naval Observatory
Science & Scientific Instruments
Science & Scientific Instruments
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Medicine and Science: Physical Sciences
Measuring & Mapping
Science & Mathematics
Data Source
National Museum of American History