Noun
the great circle on the celestial sphere midway between the celestial poles
Source: WordNetExplanatory Supplement (1992), sec. 1.233 Relationship to the celestial equator main The plane of Earth 's orbit projected in all directions forms the reference plane known as the ecliptic. Source: Internet
Celestial coordinate systems The vernal equinox occurs in March, about when the Sun crosses the celestial equator south to north. Source: Internet
Right ascension (abbreviated RA; symbol α) is the angular distance measured eastward along the celestial equator from the vernal equinox to the hour circle of the point in question. Source: Internet
Because that is when the sun crosses the celestial equator – the imaginary line in the sky above the Earth’s equator – from south to north. Source: Internet
For example, the Sun is north of the celestial equator for about 185 days of each year, and south of it for about 180 days. Source: Internet
Note that the ecliptic rotates by only about 7° during this time, whereas the celestial equator makes several complete cycles around the ecliptic. Source: Internet