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Zenith Sector

Scientific precision in 18th-century America
The zenith sector--a telescope designed to determine latitude by observing stars as they pass overhead--was the most precise geodetic instrument of the 1700s. And this zenith sector made by Philadelphia, PA inventor/surveyor/scientist David Rittenhouse was the most precise scientific instrument made in America. It served as tangible evidence that Americans could achieve the same level of technological sophistication and scientific accuracy as their European counterparts. The American zenith sector debuted in the summer of 1786, when Andrew Ellicott surveyed the boundary between the State of New York and the Commonwealth of Pennsylvania. Ellicott noted that the latitude of points along the line "may be depended on, within 2" and perhaps less."

The model for the American version was the London-made instrument used for Mason and Dixon's survey of the boundary between the colonies of Maryland and Pennsylvania.
David Rittenhouse (1732-1796)
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