The Sidereal and Tropical Zodiacs are two systems of astrological measurement. Each system has a differing foundational relationship, point of anchor and emphasis of meaning.
The Sidereal Zodiac is based in the relationship of the Earth to the Stars, anchored in the fixed stars (Spica in Libra, Aldebaran in Taurus or Antares in Scorpio, for example) and begins with Aries. The version of Sidereal Astrology promoted by Witchcrafts Artisan Alchemy uses the actual sizes and locations of the constellations as observed in the natural sky (which differs from mainstream Western and Vedic astrology). The Sidereal Zodiac attunes to vast Ages (going deeper and beyond normal correspondences of time, space and causality) and roughly aligns with the constellations throughout time (ancient and modern). The fixed nature of the Sidereal Zodiac penetrates deeper into human experience, with an emphasis on karmic cycles, eternal consciousness, real deeds and actions which impact many lifetimes, and activates the connection of earthly human consciousness with conscious intelligences throughout the cosmos.
The Tropical Zodiac is based in the relationship of the Earth to the Sun, anchored in the equinoxes (when night and day are most equal in duration) and begins at the Spring Vernal Equinox (around March 19 to 20, in Aries). The Tropical Zodiac attunes to the seasons (and their shifts) and does not align with the constellations in the modern sky. While the Tropical Zodiac roughly aligned with the constellations in 285-290 AD, in modern times there is about a 24 degree variance of constellation positions between the Sidereal and Tropical Zodiacs due to the precession of the equinoxes (also called the axial precession) caused by the tilted wobble of the earth. The zero Aries point in the Tropical system retrogrades across the sky about one degree every seventy-two years. A full revolution of this wobble takes 25,800-26,000 years. The moving nature of the Tropical Zodiac may provide fuller insight into the more transitory and temporal patterns of human experience, with an emphasis on the psychological fields of mind and emotion impacting this particular lifetime as a human creature of the Earth.