Photoheliometer

1 definition found

From The Collaborative International Dictionary of English v.0.48 [gcide]:

  Photoheliometer \Pho`to*he`li*om"e*ter\, n. [Photo- +
     heliometer.] (Astron.)
     A double-lens instrument for measuring slight variations of
     the sun's diameter by photography, utilizing the common chord
     of two overlapping images.
     [Webster 1913 Suppl.]