zenith tube

American  

noun

Astronomy.

1. a telescope mounted to point only at the zenith, used at some observatories for measuring time by the stars.

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Etymology

Origin of zenith tube

First recorded in 1830–40

Example Sentences

See Examples For:

zenith tube

In 1848 Airy invented the reflex zenith tube to replace the zenith sector previously employed.

From The Project Gutenberg Encyclopedia Volume 1 of 28 by Project Gutenberg

The instrument is now being used for investigating these variations; and in the year 1907 as many as 1,545 observations of stars were made with the reflex zenith tube.

From History of Astronomy by Forbes, George

He devised a reflex zenith tube, in which the zenith point was determined by reflection from a surface of mercury.

From History of Astronomy by Forbes, George