Sagittarius — 2nd Decan (10°–20°)
Sagittarius' second decan covers 10° to 20° of the sign. The two rulership systems keep diverging: Triplicity points to Mars, Aries' ruler, while the Chaldean system points to the Moon.
Last reviewed: 2026-07-20
Historical fact
Like every decan, this 10° segment is rooted in the ancient Egyptian system for tracking nighttime hours: 36 minor constellations that rose successively on the horizon every ten days, documented in astronomical texts from around 2100 BCE, long before their incorporation into the 12-sign zodiac in the Hellenistic period, when each sign gained three 10° decans with their own planetary rulers. At this Sagittarius decan, Triplicity and the Chaldean system continue pointing to different planets, as they already did at the previous decan.
Interpretation — Triplicity System (Modern Astrology)
In Triplicity, a Fire sign's second decan is ruled by the next same-element sign's ruler in zodiacal sequence from the original sign — for Sagittarius, that's Aries, ruled by Mars. The reading combines Sagittarius' search for meaning and wide horizons with Mars' typical assertiveness, direct action and impatience, giving the sign's idealism more urgency and drive.
Interpretation — Chaldean System (Hellenistic Tradition)
In the Chaldean system's continuous cycle, the ruler that follows Mercury — assigned to Sagittarius' first decan — is the Moon. This reading adds to Sagittarius' reach a layer of emotional sensitivity, instinct and need for comfort, a quite different combination from the martial urgency Triplicity suggests for the same degree range.
This section presents one tradition's interpretation, not a verifiable fact.
Frequently asked questions
- Why does Sagittarius' 2nd decan have different rulers in each system?
- Because Triplicity cycles through the three Fire signs (Sagittarius, Aries and Leo, in that order starting from Sagittarius), while the Chaldean system follows a continuous cycle of the 7 planets that doesn't reset at each sign. The two rarely coincide, and don't coincide at any of Sagittarius' three decans.
- What changes between Sagittarius' 1st and 2nd decan?
- The 1st decan is ruled by Jupiter under Triplicity (the sign's own ruler) and by Mercury under the Chaldean system. The 2nd shifts to Mars under Triplicity, bringing more drive and direct action, and to the Moon under the Chaldean system, bringing more emotional sensitivity.
Sources
- Nicholas Campion. A History of Western Astrology (2009).
- Claudius Ptolemy. Tetrabiblos (c. 150).
- Vettius Valens. Anthology (Hellenistic astrology) (c. 175).
- Otto Neugebauer, Richard A. Parker. Egyptian Astronomical Texts (1960).