Heliometer
Pronunciation : He`li*om"e*ter
Part of Speech : n.
Etymology : [Helio- + -meter: cf. F. h?liom?tre.] (Astron.)
Definition : Defn: 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