define celestial equator astronomy
The celestial equator is inclined by 23.4Â° to the ecliptic plane. The image shows the relations between Earth's axial tilt (or obliquity), rotation axis and plane of orbit. The celestial equator is a great circle on the imaginary celestial sphere, in the same plane as the Earth 's equator.In other words, it is a projection of the terrestrial equator out into space. As a result of the Earth's axial tilt, the celestial equator is inclined by 23.4Â° with respect to the ecliptic plane.At the poles, though, the celestial equator would be parallel to the horizon.) At all latitudes the celestial equator appears perfectly straight because the observer is only finitely far from the plane of the celestial equator but infinitely far from the celestial equator itself.