← Encyclopedia of Astrology · lesson 10/235
Decan
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What it is
Every sign of the zodiac is 30° wide. Split it into three equal parts and you have its three decans (also decanates), each 10°:
- the first decan, 0° to 10°;
- the second decan, 10° to 20°;
- the third decan, 20° to 30°.
Twelve signs times three gives thirty-six decans around the circle. Each is given a ruler of its own, a sub-ruler within the sign, which is read as adding a second colour to anything placed there. This is why astrologers sometimes say that an early Leo and a late one are not quite the same.
Two ways of assigning rulers
By planet — the faces. The older system, used from Hellenistic times through Lilly, gives each decan to one of the seven traditional planets, in the Chaldean order of their speed: Mars, Sun, Venus, Mercury, Moon, Saturn, Jupiter, and round again. The sequence starts with Mars in the first decan of Aries and runs unbroken through all thirty-six, so it ends with Mars again in the last decan of Pisces. In this system a decan is usually called a face. A few examples:
By element — the triplicity decans. The method most modern Western astrologers meet first, popularised by Alan Leo and close to the Indian drekkana, gives each decan to a sign of the same element. The first decan belongs to the sign itself, the second to the next sign of that element, the third to the last. So the decans of Aries are ruled by Aries, Leo and Sagittarius, and a third-decan Aries is read as having a touch of Sagittarius in it.
The two systems give different rulers for most decans, and astrologers simply say which they use.
How it is read
- As a nuance. A planet's decan is read as a finer shade on its sign: a Sun in the third decan of Taurus, ruled by Saturn as a face or by Capricorn by triplicity, may be read as steadier or more serious than one in the first.
- As a dignity. In traditional astrology, a planet in its own face has the smallest of the five essential dignities, worth one point in Lilly's scheme. Lilly likened a planet with nothing but face to "a man ready to be turned out of doors" — barely holding on. The face ranks below domicile, exaltation, triplicity and bounds.
- As an image. Medieval and Renaissance texts gave each decan a picture — a figure, an animal, a scene — used in talismanic magic and as an aid to description.
In the tradition
The decans are older than the zodiac's twelve signs as we know them. In Egypt, thirty-six star groups rising in turn about every ten days were used to tell the hours of the night and to mark the year of 360 days plus five. Hellenistic astrologers fitted them into the twelve signs, three to each. Ptolemy left the faces out of his scheme of dignities, but they remained part of the tradition and appear in Lilly's tables.
The decans also live on in tarot. The Hermetic Order of the Golden Dawn assigned the numbered cards from Two to Ten of each suit to the thirty-six decans, using the Chaldean planetary rulers — so the Two of Wands is Mars in Aries — and the Thoth deck carries the same scheme.
In a reading here
The essential dignity score in the structured chart report follows Lilly, counting a planet in its own face as +1, with the faces taken in the Chaldean order.