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  • WordNet 3.6
    • n heliometer 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
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Century Dictionary and Cyclopedia
    • n heliometer An astronomical instrument, consisting of a telescope having its objective sawed across in a plane passing through the optical axis, and each part arranged to move by sliding past the other, its exact position being shown by a micrometerscrew. Each half of the objective forms its own image of a star, this image moving with the half-objective which forms it. Thus, the image of one star, formed by one half of the objective, can be brought into coincidence with the image of another, formed by the other half, and by means of the micrometer the distance apart of the half-lenses, and consequently the angular distance of the two stars, can be very accurately measured, while the position-angle is determined by the direction of the line of separation of the semi lenses. This instrument is much employed in investigations into the parallax of the fixed stars, as well as for other purposes. As its name implies, it was originally devised for measuring the diameter of the sun.
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Chambers's Twentieth Century Dictionary
    • n Heliometer hē-li-om′e-tėr an instrument by which the diameters of the heavenly bodies can be measured with great accuracy
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Chambers's Twentieth Century Dictionary
Gr. hēlios, sun, metron, a measure.


In literature:

Elkin, with the Yale heliometer, obtained 0.032 of a second of arc.
"The New Heavens" by George Ellery Hale
Fraunhofer, moreover, constructed for the observatory at Koenigsberg the first really available heliometer.
"A Popular History of Astronomy During the Nineteenth Century" by Agnes M. (Agnes Mary) Clerke
He also invented a heliometer, afterwards perfected by Fraunhofer.
"Encyclopaedia Britannica, 11th Edition, Volume 4, Slice 3" by Various
They are obtained from late improved measures of the velocity of light, and from measures by the heliometer.
"Scientific American Supplement, No. 648, June 2, 1888." by Various
Nor is it difficult to imagine the probable course of reasoning which led Bessel to select the model of his new heliometer.
"Encyclopaedia Britannica, 11th Edition, Volume 13, Slice 2" by Various

In science:

Bessel, meanwhile, studied 61 Cygni with a Fraunhofer Heliometer in Königsberg, using two nearby companions.
Astrometry during the past 2000 years