Photoheliograph Lens

Photoheliograph Lens

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Description
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.
Location
Currently not on view
Object Name
Lens
date made
1874
maker
Alvan Clark & Sons
place made
United States: Massachusetts, Cambridge
Measurements
overall: 1 5/8 in x 6 in; 4.1275 cm x 15.24 cm
ID Number
PH.327710
catalog number
327710
accession number
283654
Credit Line
U.S. Naval Observatory
subject
Science & Scientific Instruments
See more items in
Medicine and Science: Physical Sciences
Data Source
National Museum of American History
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