//[astronomy](../../index.md)/[io.github.cosinekitty.astronomy](index.md)/[rotationEclEqj](rotation-ecl-eqj.md) # rotationEclEqj fun [rotationEclEqj](rotation-ecl-eqj.md)(): [RotationMatrix](-rotation-matrix/index.md) Calculates a rotation matrix from J2000 mean ecliptic (ECL) to J2000 mean equator (EQJ). This is one of the family of functions that returns a rotation matrix for converting from one orientation to another. Source: ECL = ecliptic system, using equator at J2000 epoch. Target: EQJ = equatorial system, using equator at J2000 epoch.