Work on the Tropical Zodiac

The majority of Western astrologers base their work on the tropical zodiac which divides the sky into twelve equal segments of 30 degrees each.

Beginning with the first point of Aries, the point where the line of the Earth's celestial equator and the ecliptic (the Sun's path through the sky) meet at the northern hemisphere spring equinox.

Due to the precession of the equinoxes, the slow changing of the way Earth rotates in space, the zodiacal signs in this system bear no relation to the constellations of the same name but stay aligned to the months and seasons.

Practitioners of the Vedic astrological tradition and a minority of Western astrologers use the sidereal zodiac.

This zodiac uses the same evenly divided ecliptic but approximately stays aligned to the positions of the observable constellations with the same name as the zodiacal signs.

The sidereal zodiac differs from the tropical zodiac by an offset called the ayanamsa, which steadily increases as the equinoxes drift further.

 Furthermore, some siderealists (i.e. astrologers employing sidereal techniques) use the actual, unequal constellations of the zodiac in their work.