Traditions of Astrology

There are many traditions of astrology, some of which share similar features due to the transmission of astrological doctrines between cultures. Other traditions developed in isolation and hold different doctrines, though they too share some features due to drawing on similar astronomical sources.
Vedic and Western astrology share a common ancestry as horoscopic systems of astrology, in that both traditions focus on the casting of an astrological chart or horoscope, a representation of celestial entities, for an event based on the position of the Sun, Moon, and planets at the moment of the event. However, Vedic astrology uses the sidereal zodiac, linking the signs of the zodiac to their original constellations, while
Western astrology uses the tropical zodiac. Because of the precession of the equinoxes, over the centuries the twelve zodiacal signs in Western astrology no longer correspond to the same part of the sky as their original constellations. In effect, in Western astrology the link between sign and constellation has been broken, whereas in Vedic astrology it remains of paramount importance.

Other differences between the two traditions include the use of 27 or 28 nakshatras or lunar mansions, which have been used in India since Vedic times, and the system of planetary periods known as dashas.

In Chinese astrology a quite different tradition has evolved. By contrast to Western and Indian astrology, the twelve signs of the zodiac do not divide the sky, but rather the celestial equator. The Chinese evolved a system where each sign corresponds to one of twelve 'double-hours' that govern the day, and to one of the twelve months. Each sign of the zodiac governs a different year, and combines with a system based on the five elements of Chinese cosmology to give a 60 year cycle. The term Chinese astrology is used here for convenience, but it must be recognised that versions of the same tradition exist in Korea, Japan, Vietnam, Thailand and other Asian countries.

In modern times, these traditions have come into greater contact with each other, notably with Indian and Chinese astrology having spread to the West, while awareness of Western astrology is still fairly limited in Asia. Astrology in the Western world has diversified greatly in modern times. New movements have appeared, which have jettisoned much of traditional astrology to concentrate on different approaches, such as a greater emphasis on midpoints, or a more psychological approach.