Decan, Decanate
Definition of Decan:
Based on the subdivision of a sign into three parts of 10° each. Each decan of a sign expresses subtle differences that distinguish it from the other two decans as described by its planetary sub-ruler, which operates in conjunction with the natural planetary ruler of the sign. The first decan of a sign (0°-10°) is sub-ruled by the natural ruler of the sign; the second decan (10°-20°) is sub-ruled by the ruler of the next sign in the zodiac that belongs to the same triplicity; the third decan (20°-30o) is sub-ruled by the ruler of the remaining sign in that triplicity.
An older (Chaldean) method of assigning decan sub-rulers is based upon the rulers of Planetary Hours beginning with Mars as ruler and sub-ruler of the first decan of Aries and continuing the natural order of Planetary Hours’ rulers through each successive decan, repeating as necessary until the zodiac is completed.
