太たい陽よう儀ぎ

noun

heliometer

A specialized astronomical instrument for measuring the sun's diameter or angular distances between celestial bodies. Technical term.

• 19世せい紀きの天てん文もん学がく者しゃは太たい陽よう儀ぎを使つかって太たい陽ようの直ちょっ径けいを精せい密みつに測そく定ていした。

  19th-century astronomers used a heliometer to precisely measure the sun's diameter.