celestial equator

noun Astronomy, Navigation.

1. the great circle of the celestial sphere, lying in the same plane as the earth’s equator.

noun

1. the great circle lying on the celestial sphere the plane of which is perpendicular to the line joining the north and south celestial polesAlso called: equinoctial, equinoctial circle

1. A great circle separating the northern and southern hemispheres of the celestial sphere and lying in the same plane as the Earth’s equator. The celestial equator is a projection of the Earth’s equator outward onto the celestial sphere and is used as the reference point in determining a celestial body’s declination.