Celestial equator. (n.d.). In YourDictionary. Retrieved from https://www.yourdictionary.com/celestial-equator
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.