Ecliptical length
The ecliptical longitude λ is, in addition to the ecliptical latitude β , one of the two celestial coordinates of the ecliptical coordinate system .
It counts along the ecliptic - the apparent annual path of the sun on the celestial sphere - from the spring equinox to the east, i.e. in the same sense as the change in position of the sun .
The second coordinate, latitude β, counts from the ecliptic in the direction of the ecliptic poles.
Because the earth's orbit is not exactly circular, but rather a Kepler ellipse with an eccentricity of 1.6 percent, the sun does not move completely uniformly under the stars. Their ecliptical longitude changes faster in winter than in summer (0.95 to 1.02 ° per day), which causes the so-called equation of time .
The equatorial celestial coordinates right ascension α and declination δ can be converted into the ecliptical coordinates (λ, β) using spherical trigonometry and ecliptic skew ε - with ε ≈ 23.43 ° (see small triangle on the right in the sketch). This coordinate transformation is essential for calculating the orbits of planets and other bodies in the solar system .