I first came across the idea of decanates in a book by Isabel Hickey. It's the method of splitting each sign into three sections of 10 degrees each and assigning each section a planet which then becomes a sub-ruler. This will modify or colour the sign involved. If the planet is in the first 10 degrees then the ruling planet has the full sign strength; so if we have a planet in Aries at 8 degrees, then the Aries energy will be very strong because Mars is also the sub-ruler. If the planet is at 29 degrees Aries, then it will have a Jupiter touch and the Aries nature will be more philosophical and less warlike. Here is a full breakdown of each decanate, and you should get the idea. Isabel Hickey claims the ascendant is probably the most important when looking at decanates but this method can be used for all points and planets in the chart. This system has been around for decades in its current form and can be used to gain additional insight into basic sign qualities. Obviously, it needs to be remembered that any interpretation can be affected by contradiction from elsewhere in the chart.
0-9 Mars: Honesty and directness more pronounced. Full of energy and bounce. Said to be the most innocent of the decanates. Just wants to live life.
10-19 Sun: Least self-centred decanate and has more stable energy. More inclined to fight for honour and creativity.
20-29 Jupiter: Needs movement whether mental or physical. Can be very restless, could be an explorer type. Happiest outdoors.
0-9 Venus: Very sensual and earthy. Creativity is strong. Love of beauty in all forms. Can be lazy and needs motivating but steadfast once it gets moving.
10-19 Mercury: Less stubborn and fixed. Gives more mental discrimination. Most active of decanates and needs variety.
20-29 Saturn: Can be greedy. Money and success are important. Very good at creating structures and things of long lasting value.
0-9 Mercury: The most curious and chatty but can be childlike and may never fully grow up. Never loses optimism and keeps a sunny disposition.
10-19 Venus: Can be mentally lazy but also very creative with communication. Charming and playful, likes frivolity. Needs variety. Values may fluctuate if Venus is here.
20-29 Uranus: Very detached and intellectual. Can be good with large groups. If Mercury is strong in the chart, there can be unique ideas and insights.
0-9 Moon: Can be very shy and quiet. Love of home strong. Needs to periodically retreat to clear emotions as it tends to be a bit of a sponge.
10-19 Pluto: Can be more brooding than the other decanates. Needs depth. Can be very possessive although capable of being emotionally healing for others.
20-29 Neptune: Kindness is more apparent here, strong psychic energy, very soft and mystically orientated, needs to nurture something deep inside.
0-9 Sun: Strong pride, grand gestures, powerful life force. Likes to be seen and heard. A natural performer and attention grabber. The Sun in this decanate may need encouragement to take responsibility during adulthood.
10-19 Jupiter: Most philosophical decanate. Needs to communicate the soul stuff. Must have freedom to explore ideas. Very open and honest. Could be prone to getting on the soapbox if Mercury is here.
20-29 Mars: Most restless and courageous. Independence is crucial. May see the best in everyone to their detriment. Can be blunt and willful.
0-9 Mercury: Can sometimes be the timid librarian type. Needs to make an effort to share time with others. Hermit-like behaviour on occasion, mainly because of spending too much time with their thoughts.
10-19 Saturn: Very practical and business orientated. Prone to depression but strong teaching ability due to Saturn energy and Virgo need for order and detail.
20-29 Venus: Least self-concerned and most sociable. Creativity through writing or needlework. Eye for design is very strong. Sensuality is more pronounced in this decan.
0-9 Venus: Open and friendliest of all the decanates, attracting power is strong, can draw whatever they need towards them. The planet Venus here will amplify the qualities significantly.
10-19 Uranus: The need for freedom and space, more masculine than feminine, good reasoning ability but can be dismissive of feeling.
20-29 Mercury: The talkers who can lack commitment to anything, very restless and easily bored, can be too airy at times. Can be more impartial than most.
0-9 Pluto: Very strong healing energy but also the most secretive decanate. Classic poker face type not to be taken at face value. The eyes are important.
10-19 Neptune: Will be either extremely service orientated or drain the life out of everyone around. Can be devoted to causes that better those who are stigmatised within society.
20-29 Moon: Incredible sensitivity and the softest of all the decanates. Much softer on the inside than the outer expression. May be drawn to mysticism.
0-9 Jupiter: Classic Pollyanna mentality and presentation, can't be held down for long. Tends to trot and not walk if Mercury is here. Can possess an infectious optimism.
10-19 Mars: Very cavalier attitude to life and love. Noble and confident, yet self-centred but humourous with it. Most assertive decan. Can be the knight in shining armour.
20-29 Sun: Most philosophical of all the decanates. Needs to search for the meaning of life itself. Expansive ideas and viewpoints.
0-9 Saturn: The most conservative decanate of Capricorn; can be restrictive and too serious, business orientated and does what needs to be done as a matter of duty. Reminders may be needed that love can't be ordered nor too heavily structured.
10-19 Venus: Much more relaxed than the first decanate. Can attract financial gains if the relationship between Venus and Saturn is good.
20-29 Mercury: Can be overly critical and demanding but should have good concentration, and gives self-discipline for study.
0-9 Uranus: Mad Professor decanate of the zodiac. Unique and original; not a follower of crowds but may need to learn to listen to others.
10-19 Mercury: Mentally restless and lacks fixed energy of the first decanate but much more friendly and relaxed, less stuffy. May be extremely curious about the sciences.
20-29 Venus: Needs to guard against using too much reason without considering emotions, but very good for dedicating energy to humanitarian work.
0-9 Neptune: Dreamy and mystical; needs time-out to daydream and explore the hidden layers. Never finds home on earth but learns to tolerate it.
10-19 Moon: Most moody decanate and can find it hard to detach from the environment. A very sensitive and compassionate nature towards those who are less fortunate.
20-29 Pluto: Depth, mystery, and fantasy need to be explored here, most strong willed decanate and will be either angelic or demonic.