- the angular distance of a point on the celestial sphere from the great circle that is perpendicular to the ecliptic at the point of the vernal equinox, measured through 360° eastward parallel to the ecliptic.
- the angular distance measured eastwards from the vernal equinox to the intersection of the ecliptic with the great circle passing through a celestial body and the poles of the eclipticAlso called: ecliptic longitude
- The position of a celestial object east of the vernal equinox along the ecliptic. Celestial longitude is measured in degrees eastward from the vernal equinox (0°) to the point where a great circle drawn through the object and the poles of the ecliptic intersects the ecliptic. Compare celestial latitude. See more at ecliptic coordinate system.