Precession of Earth's Axis. Slow, circular movement of Earth's poles around axis of Ecliptic at an angular distance of 23° 27'. Period of the movement is nearly 26,000 years. Caused by gravitational pull of Sun and Moon and Earth's equatorial bulge.
Precession of Equinoxes. Gradual backward movement of First Points of Aries and Libra along the Ecliptic so that their celestial longitudes are continuously decreasing.
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