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The astronomical meridian is also determined by the zenith, and is defined as a circle on the celestial sphere that passes through the zenith, nadir, and the celestial poles. A zenith telescope is a type of telescope designed to point straight up at or near the zenith, and used for precision measurement of star positions, to simplify telescope ...
The nadir [a] [b] is the direction pointing directly below a particular location; that is, it is one of two vertical directions at a specified location, orthogonal to a horizontal flat surface. The direction opposite of the nadir is the zenith .
The pole of the upper hemisphere is called the zenith and the pole of the lower hemisphere is called the nadir. [ 5 ] The following are two independent horizontal angular coordinates :
Zenith, nadir: Altitude (a) or elevation Azimuth (A) North or south point of horizon Equatorial: Center of the Earth (geocentric), or Sun (heliocentric) Celestial equator: Celestial poles: Declination (δ) Right ascension (α) or hour angle (h) March equinox: Ecliptic: Ecliptic: Ecliptic poles: Ecliptic latitude (β) Ecliptic longitude (λ ...
In astronomy, the meridian is the great circle passing through the celestial poles, as well as the zenith and nadir of an observer's location. Consequently, it contains also the north and south points on the horizon, and it is perpendicular to the celestial equator and horizon.
Groombridge transit circle of 1806. The meridian circle is an instrument for timing of the passage of stars across the local meridian, an event known as a culmination, while at the same time measuring their angular distance from the nadir.
nadir The point on the celestial sphere exactly opposite from the zenith. Thus, where the zenith is directly above an observer, the nadir is underfoot. The zenith and nadir form the two poles of the horizon line. naked eye. Also bare eye or unaided eye.
A meridian is the imaginary plane running north–south and through the zenith, nadir, and celestial poles. This is usually done with the equinox Sun at solar noon to determine the observer's latitude, but can be done with any celestial object. Solar noon is the time when the Sun crosses the meridian.