Celestial Equator

From Astrowiki-en

The projection of the Earth's equator into outer space, or to be more precise, onto the celestial sphere. The points at which the ecliptic and the celestial equator intercept are the vernal equinox and the autumnal point. The point at which the Sun crosses the celestial sphere in a northerly direction is the vernal equinox, and in a southerly direction the autumnal point (alternatively autumnal equinox).