Sidereal astrology is the practice by some western and all Indian astrologers of basing their study of the sky on the actual position of the planets in relation to the starry background. Most astrologers in the Americas and western Europe adopt the tropical zodiac approach and base their study on a notional view of the heavens which does not match the actual present positions of the stars. The sidereal zodiac is used everywhere else.

About 2,000 years ago, the two approaches were in approximate agreement. However, the tropical zodiacal system assumes that the constellations are all the same size, which they are not. Also, the tropical zodiacal system neglects the constellation of Ophiuchus, which was recognised as a constellation of the sidereal zodiac at least 1,700 years ago. Finally, due to precession of the equinoxes, there is a difference of about one zodiacal sign between the two systems

See also

• Astrology
• Zodiac
• sidereal time