An astronomical telescope designed to point vertically up to the vicinity of the zenith, used in the precise determination of star positions, astronomical latitude, and the orientation of the earth's poles.
1803
The principal instruments for a fixed observatory, are..a fixed zenith telescope, and a night telescope.
T. Cavallo, Elements Nat. or Exper. Philosophyvol. IV. 268
1938
In 1910..an order was given Mr. Gaertner for the construction of a Photographic Zenith Telescope.
W. S. Downs, Encycl. Amer. Biography New Series 364/1
2007
The only large telescope to date that uses a fixed mount..is the Large Zenith Telescope, and it uses a liquid mercury mirror.
A. T. Tokunaga & R. Jedicke in L.-A. McFadden et al., Encycl. Solar Syst. (ed. 2) xxxix. 724/1
zenith telescope typically occurs fewer than 0.01 times per million words in modern written English.
zenith telescope is in frequency band 2, which contains words occurring between 0.001 and 0.01 times per million words in modern written English. More about OED's frequency bands
Frequency data is computed programmatically, and should be regarded as an estimate.
Frequency of zenith telescope, n., 1800–2010
* Occurrences per million words in written English
Historical frequency series are derived from Google Books Ngrams (version 2), a data set based on the Google Books corpus of several million books printed in English between 1500 and 2010.
The overall frequency for a given word is calculated by summing frequencies for the main form of the word, any plural or inflected forms, and any major spelling variations.
For sets of homographs (distinct entries that share the same word-form, e.g. mole, n.¹, mole, n.², mole, n.³, etc.), we have estimated the frequency of each homograph entry as a fraction of the total Ngrams frequency for the word-form. This may result in inaccuracies.
Smoothing has been applied to series for lower-frequency words, using a moving-average algorithm. This reduces short-term fluctuations, which may be produced by variability in the content of the Google Books corpus.
Decade
Frequency per million words
1800
0.001
1810
0.0008
1820
0.0015
1830
0.0023
1840
0.0048
1850
0.0078
1860
0.017
1870
0.021
1880
0.024
1890
0.027
1900
0.028
1910
0.027
1920
0.026
1930
0.018
1940
0.015
1950
0.012
1960
0.009
1970
0.0077
1980
0.0061
1990
0.0052
2000
0.0038
2010
0.0028
Originally published as part of the entry for zenith, n. & adj.