Alcabitius Houses

Definition

Alcabitius is one of the ways of dividing a chart into twelve houses. It is named after the 10th-century Arabic astrologer al-Qabīṣī (Latinised as Alcabitius). The system takes the rising degree and measures the day-arc and night-arc it travels — the time it spends above and below the horizon — then splits each of those two arcs into equal thirds in time. The in-between house cusps are read off the zodiac at the moments those divisions produce. Where the Placidus system splits the arc of every individual degree, Alcabitius splits only the arcs of the rising degree.

In Tradition

In medieval Arabic and Latin practice, and again in the modern traditional revival, Alcabitius was the standard quadrant house system for several centuries, until Placidus displaced it. Astrologers who reconstruct medieval methods — working with Bonatti, with Lilly's pre-Placidean sources, or as traditional-revival authors reading the medieval-Latin texts on their own terms — generally use Alcabitius cusps when applying horary, electional, and natal techniques framed by Sahl, Masha'allah, Abu Ma'shar, Bonatti, or al-Qabīṣī himself.

In Practice

To work out Alcabitius cusps, software derives the day-arc and night-arc of the rising degree from sidereal time and declination, splits each one into thirds, and converts each time-third back into a zodiac position. The astrologer reads each natal planet by its Alcabitius house, alongside its whole-sign placement. For reconstructing horary and electional work, this is the right system to use when the sources cited are pre-Placidean; mixing Alcabitius cusps with Placidean reasoning, or the reverse, introduces subtle inconsistencies in primary directions and in the house-by-house readings inherited from Bonatti, Sahl, and al-Qabīṣī.

Historical Origin

The system descends from the 10th-century Arabic astrologer al-Qabīṣī (Abū al-Ṣaqr al-Qabīṣī, fl. ca. 950 CE), whose Introduction to the Art of Astrology (Kitāb al-mudkhal ilā ṣināʿat aḥkām al-nujūm) was translated into Latin as Alcabitii Introductorium by John of Seville in the 12th century and circulated widely. Bonatti's Liber Astronomiae (13th c.) explicitly carries forward al-Qabīṣī's material on Hayz, Almuguea, and Alitifal. Modern editions include the critical edition by Burnett, Yamamoto, and Yano (2004) and Dykes's English translation.

Further Reading

• Guido Bonatti, Liber Astronomiae
• Benjamin N. Dykes, Introductions to Traditional Astrology (Abu Ma'shar & al-Qabīṣī)
• Deborah Houlding, The Houses: Temples of the Sky