Bonatti's Book of Astronomy

The first-ever translation of Guido Bonatti's renowned medieval masterpiece of astrology has now sold out. But due to its importance and the level of demand, 1st-edition reprints of select Treatises are now available!

Click here for a free PDF guide to Arabic and Pahlavi vocabulary

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Download the translator's introduction as a PDF for $5:

Treatise 5

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Treatise 6

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Trs. 1-3

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Treatise 7

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Trs. 4, 8.1, 10

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Treatise 8.2

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Treatise 9

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All Treatises

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Treatise 1: Defense of Astrology
Treatise 2: Signs and Houses
Treatise 3: Planets
Treatise 4: Conjunctions
Treatise 5: 146 Considerations
Treatise 6: Questions (Horary)

Treatise 7: Elections
Treatise 8: Revolutions and Parts
Treatise 9: Nativities
Treatise 10: Weather

History of the Book of Astronomy

Guido Bonatti was one of the most famous of medieval astrologers. An advisor to important politicians in 13th Century Italy, his astrological advice influenced key events in his tumultuous times. He was so well known and influential that Dante includes him in the Inferno!

The Book of Astronomy offers an unparalleled glimpse into the working life of a medieval astrologer. For the first time, charts from Bonatti's own practice are correlated with events in his life and other political events.
Only small portions of the Book of Astronomy have ever been available in modern languages. This monumental work, several years in the making, makes the remaining 75% available. At a length of almost 1,600 pages, Bonatti's Book of Astronomy is unparalleled in traditional astrology in its size, scope, and importance. It is essential for serious students and scholars.

Table of Contents


Includes a biography of Bonatti, biographical information on his sources, essential material on sect, the al-mubtazz, whole-sign houses, "root" charts and the importance of prayer in horary, orientality, Bonatti's fixed stars, perfection in horary, the concept of "overcoming," and others. The Introduction concludes with Bonatti's own introduction and dedication to the work (65 pp). Preview

Treatise 1: Defense of Astrology

A theoretical defense of astrology which includes Bonatti's theoretical description of astrological judgment in terms of necessity, possibility, and impossibility (26 pp).

Treatise 2: Signs and Houses

Probably the most thorough treatment of the signs and houses existing in astrological literature. Drawing on many sources, Bonatti gives an explanation of the order and assignment of the signs, dignities, the weighted-point al-mubtazz, the houses and their powers, and an introduction to delineating the rulers of one house in another (121 pp). Preview

Treatise 3: Planets

Important especially for students of horary. After a thorough description of the planets' universal significations and their rulerships over hours, days, periods of life, and other matters, Bonatti turns to an account of modes of perfection. Drawing on authorities such as al-Qabisi and Abu Ma'shar, Bonatti describes numerous methods of perfection and the denial of perfection which pertain to all areas of traditional astrology. Bonatti's text is illustrated with 16 redesigned diagrams (101 pp). Preview

Treatise 4: Conjunctions

Correlates the planets to each other based on the Chaldean order; describes conjunctions pertinent to mundane astrology, especially the terrible Saturn-Mars conjunctions in Cancer; an account of the "combust hours"; concludes with a method of rectification (14 pp.)

Treatise 5: The 146 Considerations

The famous handbook of Considerations retranslated. Coley's paraphrased edition is superseded by this version, including key passages on the role of God and freedom in horary. All Arabic terms transliterated and sourced (89 pp). Preview

Treatise 6: Questions (Horary)

The most thorough treatment of horary in existence, drawing especially on the medieval masters Sahl ibn Bishr and Masha'allah. Surprising predictive techniques combine elections, solar revolutions, and horary charts. Includes two charts from Bonatti's own career. Learn whether your horse will win the race, your husband is cheating on you, or the king will fall from grace (278 pp)! Preview

Treatise 7: Elections

A long treatise on elections, often drawing on 'Ali al-Rijal (Haly Abenragel), starting with a thorough discussion on how elections work and how to design them! Elections from all 12 houses, from when to elect surgury to when to make a journey (180 pp). Preview

Treatise 8: Mundane Revolutions and Arabic Parts

First, a monumental work on mundane astrology: discovering the Lord of the Year and the Significator of the King, the condition of the people, assigning zodiacal degrees to regions of the world, weather and natural disasters, war, comets, eclipses, fixed stars, the Head and Tail of the Dragon. Second, a detailed treatment of Parts or Lots, including the 7 Hermetic Lots, the Parts of the Houses, using Parts in commodities speculation and political upheaval and regime changes. Over 100 Parts that cover all branches of astrology. Draws largely on Masha'allah and Abu Ma'shar, including a recently-identified manuscript of Abu Ma'shar (290 pp)! Preview

Treatise 9: Nativities

A treasure of natal astrology, drawing on Abu 'Ali, 'Umar al-Tabari (Omar of Tiberias), Ptolemy and al-Ridwan's commentary on the Tetrabiblos, and others. A detailed treatment of longevity calculations is followed by sections on physiognomy and personal character, and then all matters pertaining to the houses: prosperity and wealth, siblings, parents and their longevity, children, servants and illnesses, marriage and enemies, death, spirituality and travel, reputation and profession, friends, secret enemies. Lastly, Bonatti provides much information on primary directions, profections, and other predictive techniques unknown to moderns (309 pp). Preview

Treatise 10: Weather Prediction

A set of weather-predicting methods combining the mansions of the Moon (drawn from Jafar "the Indian") and Ptolemy (37 pp).

Book Reviews

I haven't felt this excited since I discovered Lilly's work...
a very powerful and emotive translation...students of horary must have this work.

- Deb Houlding,

A Masterful Translation.

- Robert Zoller

Thank you for producing such an important work forastrologers.

- Bernadette Brady

The natal treatise...did contain a whole slew of information I had not seen before...the translation is even better than billed!

- Christopher Warnock,

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