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.
写真天頂筒は、かつて国際的な緯度観測に用いられた。
The photographic zenith tube was once used for international latitude observations.
Compound of 写真 (photograph), 天頂 (zenith), and 筒 (tube). The term is a direct calque of the English 'photographic zenith tube'.