Let's talk about Decanates & how they affect the placements of your planets

decanates, or decans, are formed from the division of 3 from each zodiac sign. all of the signs have 3 decans & each of them span 10º, from 0-10, 10-20, & 20-29. each decan has a different ruler, which we call the "co-ruler" of each placement, as they all have different qualities

the most basic way we can see their effects is by looking at people born under the same sign, but not near the same date, and how they have different ways of expressing the same sign. another way they are proven to be useful is in predictive astrology & in progressed charts

before we look at the decans of each sign, you must know that there are 2 different systems of decanates, the chaldean decans, used in traditional astrology & the modern decans, used mainly in modern & vedic astrology. The difference between them being what planet rules each one

the chaldean decans are based on the 7 visible planets: the sun, moon, mercury, venus, mars, jupiter, & saturn. the modern decans are based on the ruler of the sign following whatever sign you are looking at. (ie. the decans of Aries are: mars (Aries), sun (Leo), jupiter (Sag)

here are the chaldean decans:

here are the modern decans:

now let's talk about what each planet means as the co-ruler & you can decide for yourself which system resonates more for you:

• Sun: a more yang approach. promising of personal success. directs personal energy outward. significant experiences in adulthood as pertaining to this area of life. areas of significant self-actualization & maturity

• Moon: a more yin approach. nurturing, intuitive, and feeling. directs personal energy inward. significant experiences in childhood as pertaining to the areas of the placement here. ties to past lives or accrued karma

• Mercury: more cerebral & expressive when it comes to the areas of the placement here. seeking expression, communication, and having your voice heard. intellectualized experience. seeks to express, speak out loud, or mentor/teach others with regard to the areas of the placement

• Venus: attracts others toward you for support. applies a more feeling & sensing approach. significant experiences in prepubescent, adolescence, or young adulthood pertaining to the areas of the placement here

• Mars: more willful. embodying the warrior archetype. assertive. seeking achievement here. significant experiences between ages 40-60 pertaining to the placement here

• Jupiter: born with better luck. divine blessings here. fate leans toward success in this area. significant experiences between ages 60-70 as pertaining to the placement here

• Saturn: endowed with pragmatism & common sense. may experience a "glass ceiling" with regard to the placement here. strong sense of moral duty & obligations here

• Uranus: taking the unconventional path. eccentricity in this area. standing apart from the rest. an outlier. matters revisited that come back into focus in the twilight years of life

• Neptune: more creative and intuitive in personal approach to the placement here

• Pluto: adversity brings opportunity. curveballs or crises experienced in the area of the placement here prompted by destiny lines that compel learning important karmic lessons so that you may evolve & transcend

almost forgot to include my sources:

• “The Thirty Six Decans” by Benebell Wen
• http://theastrologydictionary.com/d/decans/ 
• http://astrologyk.com/zodiac/decans 
• http://www.astrology-x-files.com/vedic/vedicastro30.html