5 articles for "Zenith"

**Zenith**[Astro*Index]

The point on the *Celestial Sphere* that is directly above an observer, defined by the intersection of a plumb bob line with the *Celestial Sphere*; thus, the pole of the circle of the horizon.

See also:

♦ Nadir ♦ Celestial Sphere

**Zenith**[Prima]

The point on the celestial sphere that is directly overhead, i.e. one pole of the axis perpendicular to the circle of the horizon. This is the geodetic zenith.

A line from the center of the Earth through the observer defines the geocentric zenith.

The angle between the geocentric zenith and the geodetic zenith is the angle of the Vertical.

The point opposite the zenith, below the horizon, is the nadir.

See also:

♦ Nadir ♦ Celestial Sphere

**Zenith**[Munkasey M.]

The North Pole in the Horizon system of co-ordinates.That point in the sky, when you are standing on the Earth and have a horizon reference in space, which is directly over your head.

See also:

♦ Nadir ♦ Celestial Sphere

**Zenith Distance**[Astro*Index]

The *angular distance* between a body and the *Zenith*.

See also:

♦ Angular Distance

**Zenith Distance**[Munkasey M.]

An arc measured in degrees along a Vertical Circle,from the Zenith downward to a predetermined point or a body.

The measurement from the pole of the Horizon system downward to another point.

The Zenith distance is mathematically equal to ninety degrees minus the altitude of a body.

Zenith distances are used in computing when different bodies rise and or set, and ar also used for twilight determinations.

**Typical Zenith distances are as follows:**

- Sunrise and Sunset: 900 50'

- Nautical Twilight: 1020

- Moonrise and Moonset: 900 50'

- Astronomical Twilight: 1080

- For the Sun at Civil Twilight: 960

See also:

♦ Angular Distance

Astro*Index Copyright © 1997 Michael Erlewine

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