Ecliptic coordinate system

Because most planets (except Mercury) and many small Solar System bodies have orbits with only slight inclinations to the ecliptic, using it as the fundamental plane is convenient.The system's origin can be the center of either the Sun or Earth, its primary direction is towards the March equinox, and it has a right-hand convention.[2] The celestial equator and the ecliptic are slowly moving due to perturbing forces on the Earth, therefore the orientation of the primary direction, their intersection at the March equinox, is not quite fixed.A slow motion of Earth's axis, precession, causes a slow, continuous turning of the coordinate system westward about the poles of the ecliptic, completing one circuit in about 26,000 years.Superimposed on this is a smaller motion of the ecliptic, and a small oscillation of the Earth's axis, nutation.[3][4] In order to reference a coordinate system which can be considered as fixed in space, these motions require specification of the equinox of a particular date, known as an epoch, when giving a position in ecliptic coordinates.[5] From antiquity through the 18th century, ecliptic longitude was commonly measured using twelve zodiacal signs, each of 30° longitude, a practice that continues in modern astrology.The signs approximately corresponded to the constellations crossed by the ecliptic.Since Leo begins 120° from the March equinox, the longitude in modern form is 139° 55′ 58″.[9] In China, ecliptic longitude is measured using 24 Solar terms, each of 15° longitude, and are used by Chinese lunisolar calendars to stay synchronized with the seasons, which is crucial for agrarian societies.A rectangular variant of ecliptic coordinates is often used in orbital calculations and simulations.The coordinates have a right-handed convention, that is, if one extends their right thumb upward, it simulates the z-axis, their extended index finger the x-axis, and the curl of the other fingers points generally in the direction of the y-axis.
Earth-centered ecliptic coordinates as seen from outside the celestial sphere .
Ecliptic longitude; measured along the ecliptic from the March equinox
Ecliptic latitude; measured perpendicular to the ecliptic
Celestial equator
A full globe is shown here, although high-latitude coordinates are seldom seen except for certain comets and asteroids .
The apparent motion of the Sun along the ecliptic (red) as seen on the inside of the celestial sphere . Ecliptic coordinates appear in (red). The celestial equator (blue) and the equatorial coordinates (blue), being inclined to the ecliptic, appear to wobble as the Sun advances.
Heliocentric ecliptic coordinates. The origin is the Sun 's center, the plane of reference is the ecliptic plane, and the primary direction (the x -axis) is the March equinox . A right-handed rule specifies a y -axis 90° to the east on the fundamental plane. The z -axis points toward the north ecliptic pole . The reference frame is relatively stationary, aligned with the March equinox.
Elliptic coordinate systemastronomycelestial coordinate systemapparent positionsorbitsSolar SystemplanetsMercurysmall Solar System bodiesinclinationseclipticfundamental planeoriginequinoxright-hand conventionsphericalrectangular coordinatesEarth-centeredcelestial sphereperpendicularCelestial equatorhigh-latitudecometsasteroidsequatorial coordinatesAxial precessionAstronomical nutationperturbing forcesorientationMarch equinoxprecessionnutationJ2000.0 epochright ascensionequatorial coordinate systemarcsecondsarcminutesecliptic polenorth ecliptic poleastronomical unitsEarth radiikilometerszodiacal signsastrologyconstellationssolar termSolar termsChinese lunisolar calendarsHeliocentricplane of referenceright-handed rulerectangular variantorbitalbarycenterright-handed conventionobliquity of the eclipticEquinox (celestial coordinates)BibcodeZodiacAstrological signsTaurusGeminiCancerScorpioSagittariusCapricornAquariusPiscesWestern astrologyElementTriplicityOphiuchusPlanets in astrologysymbolsZodiacal lightAstronomical coordinate systemsHorizontalEquatorialInvariableGalacticSupergalacticCoordinate system