Twelfth-parts, decans and fixed stars

Beneath the twelve signs lie the finer divisions that ancient astrologers weighed beside a planet's coarse sign: the thirty-six decans, the twelfth-parts, the single-degree monomoiria, the solstitial mirror-points and the bright fixed stars.

The thirty-six decans (faces)

The decans — from the Egyptian star-clocks of thirty-six ten-day asterisms rising along the ecliptic — divide each 30° sign into three 10° segments called dekanoi or prosopa (faces). In the Greek manuals two assignments appear side by side:

• The Chaldean planetary faces. Beginning with Mars in the first 10° of Aries and descending continuously through the seven planets in Chaldean order (Saturn, Jupiter, Mars, Sun, Venus, Mercury, Moon), returning to Mars in the last 10° of Pisces.
• The sign-triplicity decans. Assigning the three 10° segments of a sign to the rulers of the three signs of the same element in order.

Table of the thirty-six Chaldean decans

The twelfth-parts (dodekatemoria)

The twelfth-part divides every 30° sign into twelve micro-signs of 2°30′ each. Starting from the sign itself for the first 2°30′, each 2°30′ step advances one sign forward around the zodiac. A planet at 14° Aries stands in the sixth 2°30′ band of Aries, so its twelfth-part falls in Virgo. Ancient authors read the twelfth-part as a second, hidden placement: a planet whose twelfth-part lands on a benefic or in its own domicile carries secret support even when its coarse sign is difficult.

Paulus Alexandrinus also describes a thirteen-fold variant (multiplying the degree within the sign by thirteen instead of twelve), and Occult Astrology lets you toggle between the classic twelvefold projection and Paulus's rule.

Antiscia, monomoiria and the bright fixed stars

• Antiscia (solstitial mirror-points). Degrees equidistant from the 0° Cancer – 0° Capricorn axis share equal daylight length and "behold" one another across the solstice line: Gemini mirrors Cancer, Taurus mirrors Leo, Aries mirrors Virgo, Pisces mirrors Libra, Aquarius mirrors Scorpio and Capricorn mirrors Sagittarius.
• Monomoiria (single-degree lords). Each single degree of a sign is assigned to a planet, either ascending in Chaldean order from the sign's domicile lord or distributed by trigonal rulership.
• Bright fixed stars. Following the anonymous Greek treatise of 379 CE, bright stars of the first and second magnitude (such as Regulus, Spica, Aldebaran, Antares, Sirius, Vega and Algol) are read when rising on the Ascendant, culminating at the Midheaven, or conjoined within orb to the Sun, Moon or key lots.

How Occult Astrology shows it

Every chart includes dedicated panels for the Decans, the Twelfth-parts and antiscia, the Monomoiria and the Fixed stars, marking exact contacts on the wheel and weaving them into the reading.

Read next: the Egyptian bounds, essential dignities, or all the techniques.