The meridian on the celestial sphere. An observer's upper meridian, a semicircle, passes through their zenith and the north and south points of their horizon; the observer's local meridian is the semicircle that contains their zenith and both celestial poles.
There are several ways to divide the meridian into semicircles. In the horizontal coordinate system, the observer's meridian is divided into halves terminated by the horizon's north and south points. The observer's upper meridian passes through the zenith while the lower meridian passes through the nadir. Another way, the meridian is divided into the local meridian, the semicircle that contains the observer's zenith and both celestial poles, and the opposite semicircle, which contains the nadir and both poles.
On any given (sidereal) day/night, a celestial object will appear to drift across, or transit, the observer's upper meridian as Earth rotates, since the meridian is fixed to the local horizon. At culmination, the object contacts the upper meridian and reaches its highest point in the sky. An object's right ascension and the local sidereal time can be used to determine the time of its culmination (see hour angle).
The term meridian comes from the Latin meridies, which means both "midday" and "south", as the celestial equator appears to tilt southward from the Northern Hemisphere.
Millar, William (2006). The Amateur Astronomer's Introduction to the Celestial Sphere. Cambridge University Press.
August 26, 2023
meridian, astronomy, geographical, concept, meridian, geography, other, uses, meridian, astronomy, meridian, great, circle, passing, through, celestial, poles, well, zenith, nadir, observer, location, consequently, contains, also, north, south, points, horizon. For the geographical concept see Meridian geography For other uses see Meridian 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 Meridians celestial and geographical are determined by the pencil of planes passing through the Earth s rotation axis For a location not at a geographical pole there is a unique meridian plane in this axial pencil through that location The intersection of this plane with Earth s surface is the geographical meridian and the intersection of the plane with the celestial sphere is the celestial meridian for that location and time The meridian on the celestial sphere An observer s upper meridian a semicircle passes through their zenith and the north and south points of their horizon the observer s local meridian is the semicircle that contains their zenith and both celestial poles There are several ways to divide the meridian into semicircles In the horizontal coordinate system the observer s meridian is divided into halves terminated by the horizon s north and south points The observer s upper meridian passes through the zenith while the lower meridian passes through the nadir Another way the meridian is divided into the local meridian the semicircle that contains the observer s zenith and both celestial poles and the opposite semicircle which contains the nadir and both poles On any given sidereal day night a celestial object will appear to drift across or transit the observer s upper meridian as Earth rotates since the meridian is fixed to the local horizon At culmination the object contacts the upper meridian and reaches its highest point in the sky An object s right ascension and the local sidereal time can be used to determine the time of its culmination see hour angle The term meridian comes from the Latin meridies which means both midday and south as the celestial equator appears to tilt southward from the Northern Hemisphere See also EditMeridian geography Prime meridian planets Prime vertical the vertical circle perpendicular to a meridian Longitude planets References EditMillar William 2006 The Amateur Astronomer s Introduction to the Celestial Sphere Cambridge University Press Retrieved from https en wikipedia org w index php title Meridian astronomy amp oldid 1052624935, wikipedia, wiki, book, books, library,
