Zenith Telescope


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zenith telescope

[′zē·nəth ‚tel·ə‚skōp]
(optics)
A type of telescope that is fixed in the vertical or moves only a small amount from the vertical; it is used to get positional measurement of stars moving near the zenith.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.
The following article is from The Great Soviet Encyclopedia (1979). It might be outdated or ideologically biased.

Zenith Telescope

 

an astronomical-geodetic instrument designed to measure small differences in a star’s zenith distance. It is used for latitude determination by the Talcott method.

A zenith telescope consists of a vertically mounted refractor with an eyepiece micrometer placed in its focal plane. The central part of the telescope’s tube is attached to a horizontal axis, rotation around which helps establish the required zenith distance of the instrument’s sight line. There is a counterweight on the opposite side of the horizontal axis along with a divided circle for setting the tube at the zenith distance. The stability of the tube’s zenith distance during observation is monitored with two highly accurate levels, which are usually attached to the central part of the tube. The geographical latitude for a point of observation is computed from observations of the differences in stellar zenith distances with the necessary corrections included. The accuracy of a latitude determination (mean square error) from one observation with modern zenith telescopes is ±(0.10”-0.15”). During the late 1950’s a series of large zenith telescopes (type ZTL-180) were manufactured in the USSR with an objective measuring 18 cm in diameter and a focal length of 236 cm.

IU. I. PRODAN

The Great Soviet Encyclopedia, 3rd Edition (1970-1979). © 2010 The Gale Group, Inc. All rights reserved.
References in periodicals archive ?
As the name implies, the Large Zenith Telescope only sees the portion of the sky directly above the observatory: tipping the mirror would spill the mercury, so the liquid mirror must face straight up.
Large Zenith Telescope (LZT) 6.0 m f/1.5 Paraboloid Fixed Maple Ridge, BC, Canada 49[degrees] 17' N 122[degrees] 34' W 395 m A collaborative effort of the Univ.
* 16 visual Zenith Telescopes (ZT), Floating Zenith Telescopes (FZT) and Visual Zenith Tubes (VZT), measuring only [delta][phi]: 7 ZT at International Latitude Service stations; 2 ZT at Poltava, 1 ZT at Belgrade, Blagoveschtchensk, Irkutsk, Josefoslaw, and Pulkovo; FZT at Mizusawa; VZT at Tuorla-Turku;