on the rising decan, and the Greek system of planetary Gods, sign rulership and four elements. 2nd century BCE texts predict positions of planets in zodiac signs at the time of the rising of certain decans, particularly Sothis. The astrologer and astronomer Ptolemy lived in Alexandria. Ptolemy's work the Tetrabiblos formed the basis of Western astrology, and, "...enjoyed almost the authority of a Bible among the astrological writers of a thousand years or more." Greece and Rome The conquest of Asia by Alexander the Great exposed the Greeks to ideas from Syria, Babylon, Persia and central Asia. Around 280 BCE, Berossus, a priest of Bel from Babylon, moved to the Greek island of Kos, teaching astrology and Babylonian culture. By the 1st century BCE, there were two varieties of astrology, one using horoscopes to describe the past, present and future; the other, theurgic, emphasising the soul's ascent to the stars. Greek influence played a crucial role in the transmission of astrological theory to Rome. The first definite reference to astrology in Rome comes from the orator Cato, who in 160 BCE warned farm overseers against consulting with Chaldeans, who were described as Babylonian 'star-gazers'. Among both Greeks and Romans, Babylonia (also known as Chaldea) became so identified with astrology that 'Chaldean wisdom' became synonymous with divination using planets and stars. The 2nd-century Roman poet and satirist Juvenal complains about the pervasive influence of Chaldeans, saying, "Still more trusted are the Chaldaeans; every word uttered by the astrologer they will believe has come from Hammon's fountain." One of the first astrologers to bring Hermetic astrology to Rome was Thrasyllus, astrologer to the emperor Tiberius, the first emperor to have had a court astrologer, though his predecessor Augustus had used astrology to help legitimise his Imperial rights. Medieval world Hindu The main texts upon which classical Indian astrology is based are early medieval compilations, notably the , and Sārāvalī by . The Horāshastra is a composite work of 71 chapters, of which the first part (chapters 1–51) dates to the 7th to early 8th centuries and the second part (chapters 52–71) to the later 8th century. The Sārāvalī likewise dates to around 800 CE. English translations of these texts were published by N.N. Krishna Rau and V.B. Choudhari in 1963 and 1961, respectively. Islamic Astrology was taken up by Islamic scholars following the collapse of Alexandria to the Arabs in the 7th