The treatment of homosexuality in astrology has tended to reflect the social conditions and the attitude toward homosexuals at the time. Ptolemy, the father of Western astrology, very matter-of-factly mentions patterns that distinguish homosexuals from heterosexuals in his classic work Tetrabiblos: If Venus and Jupiter precede the Sun in a man's chart, and if the former two planets also aspect Mars, then he will be sexually interested only in other males. If, on the other hand, Mars and Venus are in masculine signs in a woman's chart, she will be inclined to lesbianism. In another place, Ptolemy notes that links between Mercury and Venus indicates an attraction to young men. This interpretation may have been suggested by the joining of the Greek names of these two planets, which results in Hermaphroditos.
By way of contrast, astrologers who matured during a period of time when society viewed homosexuality as a behavior disorder tend to attribute interest in the same sex to certain afflictions in a horoscope. Charles Carter, an important astrologer of the early twentieth century, discussed homosexuality under the heading "Immorality (Sexual)" in his Encyclopedia of Psychological Astrology. Carter saw the key to homosexuality in Uranus and Neptune. A native with a poorly aspected Uranus, particularly when Venus was involved, was thought to be a prime candidate.
As homosexuality has acquired a more acceptable position on the sexual landscape, astrological speculations that attributed same-sex preference to difficult aspects and unfavorable placements have been quietly put aside. The contemporary astrological community is highly tolerant of unconventional sexual orientations, and there now exist sun sign guides to love and romance expressly for homosexuals. There is no general agreement, however, on the process of determining sexual orientation from a birth chart. For a quick overview of astrological ideas on this subject, as well as original, research-based ninth harmonic charts consult van Dam's Astrology and Homosexuality.
Source: Lewis, James R. Astrology Encyclopedia. 2003