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Ecliptic longitude Ecliptic longitude or celestial longitude (symbols: heliocentric l, geocentric λ) measures the angular distance of an object along the ecliptic from the primary direction. Like right ascension in the equatorial coordinate system, the primary direction (0° ecliptic longitude) points from the Earth towards the Sun at the ...
The ecliptic longitudes are given in terms of a zodiac sign and a number of degrees and fractions of a degree. The zodiac signs each represent exactly 30°, starting with Aries representing longitude 0° to 30°. The degrees are added to the lower limit of the 30-degree range to obtain the longitude.
Then mean longitude is also [1] L = ϖ + M. Another form often seen is the mean longitude at epoch, ε. This is simply the mean longitude at a reference time t 0, known as the epoch. Mean longitude can then be expressed, [2] L = ε + n(t − t 0), or L = ε + nt, since t = 0 at the epoch t 0. where n is the mean angular motion and t is any ...
The heliocentric ecliptic system describes the planets' orbital movement around the Sun, and centers on the barycenter of the Solar System (i.e. very close to the center of the Sun). The system is primarily used for computing the positions of planets and other Solar System bodies, as well as defining their orbital elements .
In celestial mechanics, true longitude is the ecliptic longitude at which an orbiting body could actually be found if its inclination were zero. Together with the inclination and the ascending node , the true longitude can tell us the precise direction from the central object at which the body would be located at a particular time.
The modern definition using ecliptic longitudes, introduced by the Shixian calendar, is known as 定气法 (dìng qì fǎ, ' steady term method '). Under this method, the determination of solar terms is similar to the astronomical determination of the special cases of equinox and solstice dates, with different ecliptic longitudes to solve for.
Spherical coordinates, known as ecliptic longitude and latitude or celestial longitude and latitude, are used to specify positions of bodies on the celestial sphere with respect to the ecliptic. Longitude is measured positively eastward [6] 0° to 360° along the ecliptic from the March equinox, the same direction in which the Sun appears to ...
The plane of the Earth's orbit about the Sun is called the ecliptic, and the plane perpendicular to the rotation axis of the Earth is the equatorial plane. The angle between the ecliptic and the equatorial plane is called variously the axial tilt, the obliquity, or the inclination of the ecliptic, and it is conventionally denoted by i.