Circular micrometer

a metallic ring fixed in the focus of the object glass of a telescope, and used to determine differences of right ascension and declination between stars by observations of the times at which the stars cross the inner or outer periphery of the ring.

See also: Micrometer

Webster's Revised Unabridged Dictionary, published 1913 by G. & C. Merriam Co.

Mentioned in

Ring micrometer

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