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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 ...
Nadir also refers to the downward-facing viewing geometry of an orbiting satellite, [2] such as is employed during remote sensing of the atmosphere, as well as when an astronaut faces the Earth while performing a spacewalk. A nadir image is a satellite image or aerial photo of the Earth taken vertically.
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.
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 ...
Horizontal coordinates use a celestial sphere centered on the observer. Azimuth is measured eastward from the north point (sometimes from the south point) of the horizon; altitude is the angle above the horizon.
The solar zenith angle is the zenith angle of the sun, i.e., the angle between the sun’s rays and the vertical direction.It is the complement to the solar altitude or solar elevation, which is the altitude angle or elevation angle between the sun’s rays and a horizontal plane.
Brahma, Lord of the Zenith (center) with (from left) Varuna, Kubera, Yama and Indra. Directions in Hindu tradition are called as Diśā, or Dik. There are four cardinal directions, six orthogonal directions and a total of ten directions, however infinite combinations are possible.
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.