The sun crosses the celestial equator on March 21 and September 22.
an imaginary line circling the heavens midway between the celestial poles
The celestion equator is not a fixed object; it is more like a direction in space. Or in this case, a set of directions.
The two points where the where the celestial equator cross the ecliptic are called the vernal (or spring) and autumnal equinox. This is in relationship to the northern hemisphere but the names are...
The angle between the observer's zenith and the celestial equator is equal to the absolute value of the observer's terrestrial latitude.