Chaldean decans: the lords of all 36 decans

Chaldean decans divide every sign into three parts of ten degrees and give each part to one planet. In traditional astrology that planet is called the face, the weakest of the five essential dignities: a small, supporting claim on a stretch of the zodiac.

How the lords are assigned

The seven traditional planets follow the Chaldean order: Mars, Sun, Venus, Mercury, Moon, Saturn, Jupiter. The sequence starts at 0° Aries and runs without a break through all 36 decans. Aries takes Mars, Sun and Venus; Taurus takes Mercury, Moon and Saturn; and Pisces closes the circle with Saturn, Jupiter and Mars. Because 36 is not a multiple of seven, the pattern does not repeat inside each sign. Five signs contain their own traditional ruler among their faces: Aries, Cancer, Virgo, Scorpio and Pisces.

How to use it

Find the planet's degree: 0°00′–9°59′ is decan 1, 10°00′–19°59′ is decan 2, and 20°00′–29°59′ is decan 3. Read the sign, house and aspects first. Then check the face lord by its own sign, house and aspects, and note when the planet in the decan is the face lord itself, because it is then in its own face. The face adds a shade to the reading; it does not outweigh the sign or the house. A planet close to the boundary between two decans is better read with the neighbouring face in mind.

Other methods

The Chaldean decans are one method. The triplicity decans assign the lords another way, and for most decans the two give different planets. Choose one and keep to it in a reading.

Note on ตรียางค์

The Thai ตรียางค์ of sidereal astrology is a separate reckoning. It is worked on the sidereal zodiac, so its boundaries and lords do not match the decans described here.