Zenith sector

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(Astron.) See Sector, 3.

See also: Zenith

Webster's Revised Unabridged Dictionary, published 1913 by G. & C. Merriam Co.
References in periodicals archive ?
Two notable examples are: the 8ft mural quadrant made for the second Astronomer Royal Edmond Halley and the 12ft zenith sector device made for James Bradley, who succeeded Halley as Astronomer Royal in 1742.
p.29 La Caille used a zenith sector, not a zero sector (which latter does not exist).