Definition
The celestial equator is the projection of Earth's equatorial plane onto the celestial sphere. It divides the sky into northern and southern hemispheres and is the reference for declination (±90°).
Celestial Equator
Projection of Earth's equator onto the celestial sphere.
3D illustration
The celestial equator is tilted 23.4° from the ecliptic — the obliquity.
Use the menu and time controls to explore. Based on Jean Meeus' Astronomical Algorithms.