Zenith Telescope


Marked "Troughton & Simms, London, 1849" and "U. S. C. S. Z. T. No. 4,” this is the last of four zenith telescopes that Troughton & Simms made for the U. S. Coast Survey. It arrived in the United States in 1849, and was used for the determination of latitude by the Talcott method. .

When the Survey agreed join in the variation of latitude (polar motion) program organized by the International Geodetic Association, and found that no other instruments were available, it decided to have zenith telescopes No. 2 and No. 4 "remodeled at the Survey Office." Edwin Smith, chief of the Instrument Division, explained that "every precaution" was taken to make these instruments "as perfect as possible under the circumstances." The new features included: base and leveling screws; vertical axis; wyes for horizontal axis of telescope, with adjustment for level; larger horizontal axis for the telescope; new micrometer screw and reconstruction of micrometer box and slide; improved clamp to telescope; two fine levels attached to telescope; and a striding level for the telescope axis. The whole instrument was polished and bronzed, and provided with electric lamps and batteries "for illumination of telescope field, the reading of levels, etc." Zenith telescope No. 2 was used in Hawaii in 1891–1892, while zenith telescope No. 4 was used at Rockville, Md.

Ref: [E. Smith], "On the Variation of Latitude at Rockville, Md., as Determined from Observations Made in 1891 and 1892 in Cooperation with the International Geodetic Association," United States Coast and Geodetic Survey Report for 1892, Appendix No. 1, pp. 4–5, with illustration.

Maker: Troughton and Simms

Location: Currently not on view

Place Made: United Kingdom: England, London

See more items in: Medicine and Science: Physical Sciences, Surveying and Geodesy, Measuring & Mapping


Exhibition Location:

Related Publication: United States Coast and Geodetic Survey Report for 1892

Credit Line: U. S. Coast & Geodetic Survey

Data Source: National Museum of American History

Id Number: PH.316660Catalog Number: 316660Accession Number: 226636

Object Name: zenith telescope

Measurements: overall: 55 in x 20 in x 17 3/4 in; 139.7 cm x 50.8 cm x 45.085 cm

Guid: http://n2t.net/ark:/65665/ng49ca746ad-ee6f-704b-e053-15f76fa0b4fa

Record Id: nmah_758714

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