An Etymological Dictionary of Astronomy and Astrophysics
English-French-Persian

فرهنگ ریشه شناختی اخترشناسی-اخترفیزیک

M. Heydari-Malayeri    -    Paris Observatory

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Number of Results: 1 Search : zenithal well
zenithal well
  چاه ِ سرسویی   
câh-e sarsuyi

Fr.: puit zénithal   

1) A well used in Antiquity from bottom of which the sky could be observed during the day with a better contrast. The aperture of the well reduced the light diffused by the sky.
2) A vertical tunnel in → Paris Observatory (built in 1667), from the top roof to the underground vaults, 55m deep. This well had the purpose of observing the stars near the → zenith and measure their → parallaxes. The problem was the lack of stability of the images so that the zenithal well was hardly used. See also: → zenith telescope.

zenithal; → well.