A man uses an astrolabe to calculate the position of the stars.
A man uses an astrolabe to calculate the position of the stars.

Astrology in Arabic is ilm ahkam al-nujum, or "the science of the judgment of the stars." Although controversy exists within the Islamic world about whether it is against the laws of Islam to attempt to predict the future, for much of Islam's history astrologers were hugely influential and respected in the Muslim royal courts, developing a complex system of tools and calculations for their art.

Astrology is a Branch of Astronomy

In the Middle Ages, Islamic astronomy was very advanced in comparison to European astronomy. There was more pressure to study the movements of the sun and stars in Islamic states as opposed to Christian states because of the requirements of Islam: astrological measurements were used to calculate the direction and times in which to pray to Mecca, fix the month of Ramadan and determine the exact moments of sunrise and sunset for fasting . The importance of astrology, which was considered a specialized branch of astronomy, has its roots in the shamanistic traditions that existed in areas like Persia and India prior to Islam.

There are Three Separate Branches of Astrology

By the eighth century, three major branches of Islamic astrology had been established: Genethlialogy, which addressed individuals, astrological history, rulers and religions; catarchic astrology, which forecasted undertakings and the proper time to do things; and interrogations, which formulated responses to specific questions. Astrologers operated in bazaars, were employed in royal courts and cast horoscopes for the foundation of cities such as Baghdad.

Islamic Astrology Utilizes Specialized Instruments and Books

The three tools of the astrologer were the astrolabe, the ephemeris and the takht or dust board. The astrolabe was invented in ancient Greece, but Islamic astrologers vastly improved upon the design so that it was more accurate. The ephemeris is a table that gives the position of heavenly bodies at any given time, and the takht was a tablet covered with sand where the astrologer could make quick calculations and erase them, much like a blackboard. After taking measurements and making calculations, the astrologer would interpret these signs based on the large body of astrological literature available.

Astrological Motifs are Common in Islamic Art

One of the most interesting things to develop out of Islamic astrology was the use of astrological images in Islamic art. These images were derived from ancient Greek descriptions of constellations -- for example, scales for Libra and a ram for Aries -- and were used as talismanic symbols on objects such as bowls, flasks and inkwells. It was believed that, through these images, the occult powers of the stars could be harnessed and used to protect the owner of the object. Artists even personified the planets into human figures based on the Greek pantheon.