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Encyclopedia > Celestial coordinate system

In astronomy, a celestial coordinate system is a coordinate system for mapping positions in the sky. There are different celestial coordinate systems each using a coordinate grid projected on the celestial sphere, in analogy to the geographic coordinate system used on the surface of the Earth. The coordinate systems differ only in their choice of the fundamental plane, which divides the sky into two equal hemispheres along a great circle. (The fundamental plane of the geographic system is the Earth's equator). Each coordinate system is named for its choice of fundamental plane; below the name of a pole and the names of the coordinates are also shown: Radio telescopes are among many different tools used by astronomers Astronomy (Greek: Î±ÏƒÏ„ÏÎ¿Î½Î¿Î¼Î¯Î± = Î¬ÏƒÏ„ÏÎ¿Î½ + Î½ÏŒÎ¼Î¿Ï‚, astronomia = astron + nomos, literally, law of the stars) is the science of celestial objects and phenomena that originate outside the Earths atmosphere, such as stars, planets, comets, auroras, galaxies, and the cosmic background radiation. ... In mathematics as applied to geometry, physics or engineering, a coordinate system is a system for assigning a tuple of numbers to each point in an n-dimensional space. ... The celestial sphere is divided by the celestial equator. ... Map of Earth showing lines of latitude (horizontally) and longitude (vertically); large version (pdf) The geographic (earth-mapping) coordinate system expresses every horizontal position on Earth by two of the three coordinates of a spherical coordinate system which is aligned with the spin axis of the Earth. ... Earth (often referred to as The Earth) is the third planet in the solar system in terms of distance from the Sun, and the fifth in order of size. ... The fundamental plane in a spherical coordinate system is a plane which divides the sphere into two hemispheres. ... A sphere (< Greek ÏƒÏ†Î±Î¯ÏÎ±) is a perfectly symmetrical geometrical object. ... For the Brisbane bus routes known collectively as the Great Circle Line (598 & 599), see the following list of Brisbane Transport routes A great circle on a sphere A great circle is a circle on the surface of a sphere that has the same diameter as the sphere, dividing the... The equator is an imaginary circle drawn around a planet (or other astronomical object) at a distance halfway between the poles. ...

The horizontal coordinate system is a celestial coordinate system that uses the observers local horizon as the fundamental plane. ... Horizon The horizon is the line that separates earth from sky. ... The zenith, in astronomy, is the point in the sky which appears directly above the observer. ... The nadir (from Arabic nazir, opposite) is the astronomical term for the point in the sky directly below the observer, or more precisely, the point in the sky with an inclination of -90Â°. Geometrically, it is the point on the celestial sphere intersected by a line drawn from the observer... In astronomy and surveying, altitude (sometimes called elevation) is one of the two coordinates of the horizontal coordinate system, and refers to the vertical angle from the horizon. ... Azimuth is the horizontal component of a direction (compass direction), measured around the horizon toward the East, i. ... The equatorial coordinate system is probably the most widely used celestial coordinate system, whose equatorial coordinates are: declination () right ascension () -also RA-, or hour angle () -also HA- It is the most closely related to the geographic coordinate system, because they use the same fundamental plane, and the same poles. ... The celestial equator is a great circle on the imaginary celestial sphere, which could be constructed by inflating the Earths equator until it intersects with said sphere. ... The two celestial poles are the imaginary points where the Earths spin axis intersects the imaginary rotating sphere of gigantic radius, called the celestial sphere. ... In astronomy, declination (dec) is one of the two coordinates of the equatorial coordinate system, the other being either right ascension or hour angle. ... Right ascension (RA; symbol Î±: Greek letter alpha) is the astronomical term for one of the two coordinates of a point on the celestial sphere when using the equatorial coordinate system. ... In astronomy, an objects hour angle (HA) is defined as the difference between the current local sidereal time (LST) and the right ascension () of the object: HAobject = LST - object Thus, the objects hour angle indicates how much sidereal time has passed since the object was on the local... The B1950. ... The J2000. ... The ecliptic coordinate system is a celestial coordinate system that uses the ecliptic for its fundamental plane. ... The plane of the ecliptic is well seen in this picture from the 1994 lunar prospecting Clementine spacecraft. ... Ecliptic latitude is one of the co-ordinates which can be used to define the location of an astronomical object on the celestial sphere in ecliptic coordinates. ... Ecliptic longitude (celestial longitude) is one of the co-ordinates which can be used to define the location of an astronomical object on the celestial sphere in ecliptic coordinates. ... Many galaxies, including the Milky Way in which our Sun and Earth are located, are disk-shaped: the majority of their visible mass (excluding possible dark matter) lies very close to a plane. ... Supergalactic coordinates are coordinates in a spherical coordinate system which was designed to have its equator aligned with the supergalactic plane, a major structure in the local universe formed by the preferential distribution of nearby galaxy clusters (such as the Virgo cluster, the Great Attractor and the Pisces-Perseus supercluster...

Equatorial to Horizontal coordinates

Let δ be the declination and H the hour angle. In astronomy, declination (dec) is one of the two coordinates of the equatorial coordinate system, the other being either right ascension or hour angle. ... In astronomy, an objects hour angle (HA) is defined as the difference between the current local sidereal time (LST) and the right ascension () of the object: HAobject = LST - object Thus, the objects hour angle indicates how much sidereal time has passed since the object was on the local...

Let φ be the observer's latitude. Latitude, usually denoted symbolically by the Greek letter Ï†, gives the location of a place on Earth north or south of the Equator. ...

Let Alt be the altitude and Az the azimuth. In astronomy and surveying, altitude (sometimes called elevation) is one of the two coordinates of the horizontal coordinate system, and refers to the vertical angle from the horizon. ... Azimuth is the horizontal component of a direction (compass direction), measured around the horizon toward the East, i. ...

Then the equations of the transformation are: $sin Alt = sin phi cdot sin delta + cos phi cdot cos delta cdot cos H$

Use the inverse trigonometric functions to get the values of the coordinates. In mathematics, the trigonometric functions are functions of an angle, important when studying triangles and modeling periodic phenomena. ...

This article originates from Jason Harris' Astroinfo which comes along with KStars, a Desktop Planetarium for Linux/KDE. See http://edu.kde.org/kstars/index.phtml Screenshot of KStars showing the night sky from Hanover. ... Linux (also known as GNU/Linux) is a computer operating system. ... KDE (K Desktop Environment) is a free desktop environment and development platform built with Trolltechs Qt toolkit. ... Results from FactBites:

 NationMaster - Encyclopedia: Right ascension (1321 words) The celestial sphere is divided by the celestial equator. RA is the celestial equivalent of terrestrial longitude. The ecliptic coordinate system is a celestial coordinate system that uses the ecliptic for its fundamental plane.
 Basic Astronomical Terms (939 words) Celestial coordinate corresponding to latitude in the equatorial celestial coordinate system. Celestial coordinate corresponding to longitude in the equatorial celestial coordinate system. The celestial coordinate corresponding to latitude is the Declination.
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