Zenith

1. That point in the visible celestial hemisphere which is vertical to the spectator; the point of the heavens directly overhead; -- opposed to nadir.
2. hence, figuratively, the point of culmination; the greatest height; the height of success or prosperity.
Zenith distance . (Astron.)
See under Distance.
Zenith sector . (Astron.)
See Sector, 3.
Zenith telescope (Geodesy),
a telescope specially designed for determining the latitude by means of any two stars which pass the meridian about the same time, and at nearly equal distances from the zenith, but on opposite sides of it. It turns both on a vertical and a horizontal axis, is provided with a graduated vertical semicircle, and a level for setting it to a given zenith distance, and with a micrometer for measuring the difference of the zenith distances of the two stars.