Triplicity decans: sub-signs and lords of all 36 decans

Triplicity decans divide every sign into three parts of ten degrees and give the parts to the three signs of the same element. The first part belongs to the sign itself; the second and third belong to the other two signs of its element. Each part is ruled by the traditional ruler of that sub-sign.

How the lords are assigned

The signs of one element sit four signs apart around the zodiac: Aries, Leo and Sagittarius for fire, and likewise for earth, air and water. Each sign starts with itself, then takes the next two signs of its element in zodiac order, wrapping from the last back to the first. Aries runs Aries, Leo, Sagittarius. So Aries decan 2 has Leo as its sub-sign and the Sun as lord. For Scorpio, Aquarius and Pisces the lords are the traditional rulers, Mars, Saturn and Jupiter; a modern variant would name Pluto, Uranus and Neptune.

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 add the tint of the sub-sign and check the lord by its own sign, house and aspects. This refines the flavour. It is not one of the five essential dignities and does not change how a planet stands in its sign.

Not to be confused with

The triplicity decan is a different thing from the triplicity ruler (ดาวเจ้าธาตุ), the essential dignity that gives each element a day, a night and a participating ruler. It is also a different method from the Chaldean decans: for most decans the two give different planets, so 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.