Decanate, Decan

A term applied to a subdivision of Sign into 10° arcs, referred to as the first, second and third decanates or decans. The interpretation of Decans is based upon a system of rulerships, of which there are two in common use. One method ascribed Mars to the first Decan of Aries and thence carried a fixed series throughout the 36 Decans, ending again with Mars ruling the third Decan of Pisces. The series is Mars, Sun, Venus, Mercury, Moon, Saturn, Jupiter; as follows:

The other method employs the Ruler of the Sign as specifically the Ruler of the First Decan, with the Second and Third Decans associated with the Rulers of the other two Signs of the same triplicity. Thus the First or Aries Decan of Aries is ruled by Mars; the Second or Leo Decan, by the Sun; and the Third or Sagittarian Decan, by Jupiter. This gives this series:-