The (RA, Dec) system fixed to Earth's equator and the vernal equinox.
Definition
The equatorial system uses the celestial equator as the primary great circle and the vernal equinox as origin. Coordinates may be referred to the mean equator of a standard epoch (e.g. J2000.0) or the true equator of date (including nutation).
3D illustration
Equatorial grid on the local sky — RA and declination.
Use the menu and time controls to explore. Based on Jean Meeus' Astronomical Algorithms.
