Astronomical elements
Astronomical elements are selected intangible objects of a geometric nature. They are used to define astronomical coordinate systems and their position in relation to one another, to convert the coordinates , to reference and calculate orbit elements and orbit data of an object, the time of astronomical events and the movements and positions relative to the observer's point of view ( ephemeris ). Computationally, however, they are treated in the same way as material objects. A special example are the Bessel elements : Cartesian coordinates of a straight line through the centers of two celestial bodies in a special coordinate system with origin in the center of the earth ( Bessel's fundamental system ) and the size and cone angle of the shadow that is created by the covering of the more distant celestial body.
- Center of the earth , barycentre of systems, center of gravity of middle and true objects, galactic center
- Main positions: equinoxes (spring point, autumn point), solstices (solstices: summer solstice, winter solstice), apses (apoapsis, periapsis), knots (especially the lunar knot ), culmination point , constellations : conjunction , opposition ( syzygium ), e.g. B. Full moon , new moon .
- Poles ( ecliptic poles , celestial poles , zenith , nadir ), cardinal points ( south point , north point , east point , west point )
Reference lines:
- Solstitiallinie , Apsides , nodal line , the Earth's axis , Kolur
- Line of sight (gaze direction) or , draw attention , plumb
- ideal and osculating curves ( conforming to the currently known value)
- Orbit ( orbit ), Kepler orbit , hodograph
- Levels that describe the mean states of disturbed paths , the layers of an object or other data
- Galactic plane , ecliptic , orbital plane ; Equatorial plane ( celestial equator ), horizon , meridian plane
- Bodies that are generally used to define idealized mean objects :
- Earth ellipsoid , geoid , solenoid , spheroid