In astrology, a decan is the subdivision of a sign. In order to give fuller interpretation to the zodiac signs, ancient astrologers subdivided each sign into periods of approximately ten days. These divisions are known as the "decans" or "decanates" and cover modifications of individual traits, attributed to minor planetary influences, which temper or blend with the ruling influence of the period. The ten-day spans are somewhat arbitrary in order to allow for the five (and sometimes six) extra days in the year beyond the 360 days required for the thirty-six decans.
Each sign is allocated a triplicity, consisting of three of the four classical elements air, water, earth or fire, and is therefore subdivided into three equal parts of 10 degrees each; these parts are referred to as decans or decanates.
Each decan of a sign is assigned rulership by the planet ruling the sign and secondary rulership by the planet ruling the decan.
In Ptolemy The decans and their rulers are assigned as follows as based on the description by the Alexandrian Egyptian astrologer, Ptolemy, from whose Tetrabiblos are derived most of the principles of western astrology:
Sign Domicile ruler Exaltation ruler 0–10 degrees 10–20 degrees 20–30 degrees Aries Mars Sun Mars Sun Venus Taurus Venus Moon Mercury Moon Saturn Gemini Mercury N/A Jupiter Mars Sun Cancer Moon Jupiter Venus Mercury Moon Leo Sun N/A Saturn Jupiter Mars Virgo Mercury Mercury Sun Venus Mercury Libra Venus Saturn Moon Saturn Jupiter Scorpio Mars N/A Mars Sun Venus Sagittarius Jupiter N/A Mercury Moon Saturn Capricorn Saturn Mars Jupiter Mars Sun Aquarius Saturn N/A Venus Mercury Moon Pisces Jupiter Venus Saturn Jupiter Mars
Traditional Chaldean rulerships
+"The Faces of the Planets" * (Lilly) Sign First Decan ruler (0–9.999 deg.) Second Decan ruler (10–19.999 deg.) Third Decan ruler (20–29.999 deg.) Aries Mars Sun Venus Taurus Mercury Moon Saturn Gemini Jupiter Mars Sun Cancer Venus Mercury Moon Leo Saturn Jupiter Mars Virgo Sun Venus Mercury Libra Moon Saturn Jupiter Scorpio Mars Sun Venus Sagittarius Mercury Moon Saturn Capricorn Jupiter Mars Sun Aquarius Venus Mercury Moon Pisces Saturn Jupiter Mars * as used as an essential dignity in astrology.
Notice that rulerships follow a repeating pattern, the Chaldaean order of the planets: Saturn, Jupiter, Mars, Sun, Venus, Mercury, Moon, based on a geocentric cosmological model.
Modern rulerships Modern astrology updates the rulerships. Decans or "faces" are the least important of the essential dignities, representing about one-fifteenth of a planet's overall strength in medieval astrology.
The decans and their rulers are assigned as follows as based on the concepts of modern Western astrology :
Sign 1st decan ruler 2nd decan ruler 3rd decan ruler Aries Mars Sun Jupiter Taurus Venus Mercury Saturn Gemini Mercury Venus Uranus Cancer Moon Pluto Neptune Leo Sun Jupiter Mars Virgo Mercury Saturn Venus Libra Venus Uranus Mercury Scorpio Pluto Neptune Moon Sagittarius Jupiter Mars Sun Capricorn Saturn Venus Mercury Aquarius Uranus Mercury Venus Pisces Neptune Moon Pluto
See also Decans in the Chinese zodiac
Citations
References
Further reading
External links Image for the Third Face of Aries, an example of a decan talisman using traditional astrology.