Encyclopædia Galactica Rami T. F. Rekola Tuorlan Astronomical Society Tuorla Observatory University of Turku

CooC - Coordinate Conversions (version 3.0)

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Ecliptic coordinate systems

Primarily for studies of objects within the solar system the most logical reference plane is that of the ecliptic. All planets have their orbital planes at almost the same level, but the plane of the ecliptic has been determined from the orbital plane of the Earth (not surprisingly).

Ecliptic longitude, [lambda], is measured counterclockwise from the direction of the northern vernal equinox (the point at which the ecliptic and the celestial equator intersect). The values are between 0 and 360 degrees in decimal format (degrees).

Ecliptic latitude, [beta], is measured from the plane of the ecliptic, positive northwards and negative southwards. The values are between -90 and +90 degrees in decimal format (degrees).

Heliocentric ecliptic coordinates have their point of origin in the centre of the Sun.

Geocentric ecliptic coordinates have their point of origin in the centre of the Earth.

Topocentric ecliptic coordinates have their point of origin at a geographic location on the surface of the Earth.

The difference of these three ecliptic coordinate systems is infinitesimally small for objects outside of our solar system and impossible to measure for extragalactic objects. However, for solar system objects, and especially objects in the vicinity of the Earth, such as satellites and the Moon, the three coordinates may be remarkably different.

For more information on different coordinate systems, please check the corresponding encyclopædia article.




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