Photoheliograph Lens

Photoheliograph Lens

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Usage conditions apply
Hoping to improve our understanding of the distance between the Earth and the Sun, the United States sponsored eight parties to observe the 1874 transit of Venus across the face of the sun, and equipped each with an identical set of apparatus made by Alvan Clark & Sons. For photographing the sun, each party had a horizontal telescope—known as a photoheliograph—with a lens of 5-inches aperture and nearly 40 feet focal length. This is one of those lenses. The “Kerguelen” inscription on the cell indicates that this lens was used at the observing station on a Kerguelan island in the southern Indian Ocean.
Ref: Simon Newcomb, ed., Observations of the Transit of Venus, December 8-9, 1874 (Washington, D.C., 1880), pp. 25-26.
Currently not on view
Object Name
date made
Alvan Clark & Sons
place made
United States: Massachusetts, Cambridge
overall: 1 5/8 in x 6 in; 4.1275 cm x 15.24 cm
ID Number
catalog number
accession number
Credit Line
U.S. Naval Observatory
Science & Scientific Instruments
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Medicine and Science: Physical Sciences
Data Source
National Museum of American History
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