写しゃ真しん天てん頂ちょう筒とう

noun

photographic zenith tube

A specialized astronomical instrument used to determine the zenith point by photographing stars near the zenith. Technical term in astrometry and geodesy.

• 写しゃ真しん天てん頂ちょう筒とうは、かつて国こく際さい的てきな緯い度ど観かん測そくに用もちいられた。

  The photographic zenith tube was once used for international latitude observations.