You searched for: “heliometer”
heliometer (s) (noun), heliometers (pl)
An instrument devised originally for measuring the diameter of the sun; now it is 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.
This entry is located in the following units: helio-, heli- (page 2) meter-, metro-, metr-, -metrical, -metrically, -metron, -metric, -metrist, -meter, -meters, -metry, -metre (page 17)