Great Conjunction

Definition

A Great Conjunction is a conjunction of Jupiter and Saturn — the two slowest naked-eye planets meeting in the same place in the sky. It happens roughly every 19.86 years, about every 20 years, and mundane astrology uses it as the chief marker of long-term historical cycles. Each conjunction lands about 117° further along the zodiac than the last, so a run of them falls in signs of the same element for roughly 200–240 years before stepping into the next element — a change called the Great Mutation.

In Tradition

In the medieval Arabic-Persian and Latin tradition, Jupiter-Saturn great conjunctions are the master cycle of mundane astrology, nested at three scales: 20-year sub-cycles, the ~240-year triplicity periods (the great conjunctions themselves), and the ~960-year returns through all four elements, the conjunctio maxima. Sahl ibn Bishr and Abu Maʿshar codify the doctrine, Bonatti and the Latin-medieval tradition carry it forward, and modern mundane astrologers keep the cycle as their standard long-arc framework.

In Practice

A mundane astrologer casts several charts: (1) the chart of each Great Conjunction for the relevant capital cities; (2) the chart of each Great Mutation, the triplicity-shift, as a marker of a roughly 240-year era; and (3) ingress and eclipse charts within the prevailing conjunction era for finer timing. The 21 December 2020 conjunction at 0°29′ Aquarius marked the move out of the earth-element sequence that had run since 1842 and into the air element — in the standard reckoning, the start of the next 240-year era. The significations are read collectively: the house position locates the affected matter, the sign sets the style and theme, and hard aspects to the outer planets sharpen the timing of major shifts. This is the slowest-moving naked-eye cycle in classical astrology.

Historical Origin

Babylonian astronomers already tracked Saturn-Jupiter cycles within the broader period-relations of the Goal-Year texts. Sahl ibn Bishr's 9th-c. *Introduction* discusses the great-conjunction triplicity-change doctrine; Abu Maʿshar's *Kitāb al-qirānāt*, or *On the Great Conjunctions* (9th c.), is the systematic treatment, transmitted to Latin by Hermann of Carinthia and John of Seville (12th c.) and reused by Bonatti, Pierre d'Ailly, and later Kepler in his *De Stella nova* (1606).

Further Reading

• Abu Maʿshar / Benjamin Dykes (trans.), On the Great Conjunctions
• Guido Bonatti, Liber Astronomiae
• Nicholas Campion, A History of Western Astrology