HELIOMETER

heliometer

(noun) an instrument used to measure the angular separation of two stars that are too far apart to be included in the field of view of an ordinary telescope

Source: WordNet® 3.1

Etymology

Noun

heliometer (plural heliometers)

An astronomical instrument, based on a telescope, for measuring the diameter of the sun; now used to measure the angular distance between stars and other celestial bodies.

Source: Wiktionary

He`li*om"e*ter, n. Etym: [Helio- + -meter: cf. F. héliomètre.] (Astron.)

Definition: An instrument devised originally for measuring the diameter of the sun; now employed for delicate measurements of the distance and relative direction of two stars too far apart to be easily measured in the field of view of an ordinary telescope.

Source: Webster’s Unabridged Dictionary 1913 Edition