text: As the rotational axis of the Earth is not perpendicular to its orbital plane , the equatorial plane is not parallel to the ecliptic plane , but makes an angle of about 23 Â 26 ' , which is known as the axial tilt ( or obliquity of the ecliptic ) .
simplified: The ecliptic plane should be distinguished from the invariable ecliptic plane , which is perpendicular to the vector sum of the angular momenta of all planetary orbital planes , to which Jupiter is the main contributor . The present ecliptic plane is inclined to the invariable ecliptic plane by about 1.5 Â .