Traditions
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 completely different doctrines, although they too share some similar features due to the fact that they are drawing on similar astronomical sources.
Current traditions
The main traditions used by modern astrologers are:
- Chinese astrology
- Jyotisha, Indian or Vedic astrology
- Western astrology
Western and Indian astrology share a common ancestry as horoscopic systems of astrology and are essentially similar in content. 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. The main difference between the two traditions is that Indian astrology continues to use the sidereal zodiac, linking the signs of the zodiac to their original constellations, while Western astrology uses the tropical zodiac (see section below). Because of the phenomenon 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 (and so to their Indian counterparts). In effect, in Western astrology the link between sign and constellation has been broken, whereas in Indian astrology it remains of paramount importance.
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. Also most notably and uniquely, 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 (12 x 5) year cycle. The term Chinese astrology is used here for convenience, but it must be recognised that versions of the same tradition exist in Japan, Vietnam, Thailand and other East Asian countries.
In modern times, the three traditions have come into greater contact with each other. Chinese and Indian astrology have spread to the West, and awareness of Western astrology has increased in India and East Asia
