Converts a J2000 mean equator (EQJ) vector to a true ecliptic of date (ETC) vector and angles.
Given coordinates relative to the Earth's equator at J2000 (the instant of noon UTC
on 1 January 2000), this function converts those coordinates to true ecliptic coordinates
that are relative to the plane of the Earth's orbit around the Sun on that date.
Converts a J2000 mean equator (EQJ) vector to a true ecliptic of date (ETC) vector and angles.
Given coordinates relative to the Earth's equator at J2000 (the instant of noon UTC on 1 January 2000), this function converts those coordinates to true ecliptic coordinates that are relative to the plane of the Earth's orbit around the Sun on that date.