a telescope mounted to point only at the zenith, used at some observatories for measuring time by the stars.
When Does Summer Really End?So when the rest and relaxation is shooed away for cooler days and the start of school, it’s easy to forget that the summer season is far from over.
Origin of zenith tube
First recorded in 1830–40
Also called zenith telescope.
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019