Telescope
date: label: date made
content: ca 1880
notes: label: Description
content: Seth Chandler earned his living as an actuary but made his mark as an astronomer. His most important scientific achievement was the discovery of what became known as polar motion, the wobble of the Earth around its axis of rotation. He observed this phenomenon with a zenith telescope of his own design—which he called an "almucantar"—for viewing stars as they passed overhead. After the first example proved promising, he had a larger one made.
label: Description
content: This telescope, which came from Chandler’s home in Vermont, does not seem to be either of the almucantars described in his scientific papers, but may have been part of the instrument for which he obtained a patent in 1881.
label: Description
content: It has a cylindrical draw-tube telescope made of brass that measures 22¾ inches long when closed. The objective lens has a clear aperture of 2 inches. The tube is blackened on the inside, and has no internal diaphragms.
label: Description
content: The lenses may have been figured by John Clacey, an optical instrument maker who worked in Cambridge, Ma., in the late 1870s, and who is credited with having made the optical elements of Chandler’s almucantars.
label: Description
content: Ref: Seth Chandler, "Altitude Instrument," U.S. Patent 239,315 (1881).
label: Description
content: Seth Chandler, “The Almucantar. An Investigation Made at the Observatory in 1884 and 1885,” <i>Annals of the Harvard College Observatory</i> 17 (1887): 1-222.
label: Description
content: W. E. Carter and M. S. Carter, “Seth Carlo Chandler, Jr.,” <i>Biographical Memoirs of the National Academy of Sciences</i> (1995): 45-79.
label: Description
content: “John Clacey—Optician,” <i>Popular Astronomy</i> 38 (1930): 472-477.
label: Location
content: Currently not on view
setName: label: See more items in
content: Medicine and Science: Physical Sciences
label: See more items in
content: Science & Mathematics
dataSource: label: Data Source
content: National Museum of American History
identifier: label: ID Number
content: 1980.0709.02
label: accession number
content: 1980.0709
label: catalog number
content: 1980.0709.02
objectType: label: Object Name
content: telescope
label: Object Name
content: telescope, refracting
physicalDescription: label: Physical Description
content: brass (overall material)
label: Measurements
content: overall: 23 3/4 in x 2 1/2 in; 60.325 cm x 6.35 cm
label: Measurements
content: overall: 23 5/8 in x 2 1/2 in; 60.0075 cm x 6.35 cm