Each year as the Sun moves around the ecliptic its right ascension and declination vary as shown in the above table. In each instance the altitude of the NCP has been drawn equal to the latitude since the two are always numerically equal. On the dates of the equinoxes , when the Sun's declination is 0 degrees, its daily path is along the celestial equator. Daylight lasts 24 hours. The night is 24 hours long.
Days are shorter than nights.
But between September 21 and March 21, when the Sun's declination is negative, it is always below the horizon. In other words day and night are both six months long. Thus, half the sky above the horizon is always visible and the other half below the horizon is never seen. Also, the equator is the only place where the Sun is at the zenith at noon on the dates of the equinoxes. At the equator, not only the Sun but all celestial objects rise and set vertically to the horizon.