The Rulers of the Decans: Astrology's Secret Layer Hiding In Plain Sight
You've finally got your head round houses, signs, aspects. Perhaps you've even mastered the whole ascendant-descendant thing without your brain melting. Then someone mentions decans and their rulers, and suddenly you're back to square one.
Scary.
Here's the thing though: decans or "faces" are the least important of the essential dignities, representing about one-fifteenth of a planet's overall strength in medieval astrology. So why bother learning them? Because sometimes—not always, but sometimes—they're precisely what fills in the missing detail that makes a chart make sense.
What Actually Is a Decan?
In order to give fuller interpretation to the zodiac signs, ancient astrologers subdivided each sign into periods of approximately ten days. Each zodiac sign spans 30 degrees. Divide that by three and you get 10-degree chunks. Those chunks? They're your decans.
Each decan has a ruler which becomes the sub ruler of the sign or the co-ruler of that sign. It's like a supporting actor who adds flavour to the main star's performance.
If you've ever wondered why your mate Sarah, born in early Aries, is nothing like your other mate Jake, born in late Aries, even though they're both technically Aries? Decans. That's your answer right there.
The Egyptian Origins Nobody Talks About Anymore
Before the Greeks got their hands on this system, the Egyptians were already dividing the sky into 36 star groups. Decans first appeared in the First Intermediate Period of Egypt on coffin lids—yes, coffin lids—from around 2100 BC.
The sequence of these star patterns began with Sirius ("Sothis"), and each decan contained a set of stars and corresponding divinities. The Egyptians used them to tell time at night. Brilliant, when you think about it—no smartphones, no watches, just stars and a coffin lid with a map painted on the inside.
As measures of time, the rising and setting of decans marked 'hours' and groups of ten days, which comprised an Egyptian year. Thirty-six decans times ten days equals 360 days. Add five extra days and you've got yourself a year.
Two Systems, One Massive Headache
Right, here's where it gets messy. There are two main systems for assigning planetary rulers to the decans, and astrologers argue about which one's "correct" with the passion usually reserved for football rivalries.
The Chaldean Order: The Old Guard
This system—also called the Ptolemaic order—arranges planets from slowest to fastest as they appeared to ancient sky-watchers standing on Earth. The Chaldean Order follows as such: Moon - Mercury - Venus - Sun - Mars - Jupiter - Saturn.
Wait, that's backwards from what I just said, right? That's because the decans as they're arranged around the zodiac are in descending Chaldean Order, meaning they go from slowest orbit to fastest orbit, beginning with Mars in Aries.
At Wilfred Hazelwood, we've noticed that traditional astrologers tend to swear by this system. So in traditional and Horary Astrology, the decans are often called "faces" and each 10-degree segment of a sign has a different planetary ruler (according to the Chaldean Order).
These Chaldean decans were taught by the Greco-Egyptian astrologer known as Taucer of Babylon in the 3rd century, Roman astrologer Firmicus in the 4th century, and the Arabic astrologer Abu Ma'shar in the 9th century. That's a proper pedigree.
The Triplicity System: The Modern Upstart
Then along came British astrologer Alan Leo in the 20th century and shook things up. His system works differently.
In the so-called Triplicity system commonly used in Modern Astrology the first decan of any sign is the ruler of the whole sign. Then you look at the element (fire, earth, air, water) and assign rulers based on the other signs in that same element.
Take Aries. Fire sign, ruled by Mars. The first decan of Aries is Aries, ruled by Mars. The second decan is Leo, ruled by the Sun, the next fire sign in the zodiac. So the second decan of Aries is ruled by the Sun. The third decan of Aries would be the next fire sign after Leo, which is Sagittarius, ruled by Jupiter.
Clean. Logical. Easy to remember. Which is probably why in modern astrology the second method appears to have more widespread acceptance than the first.
Why This Actually Matters (Beyond Showing Off At Parties)
"Alright, Claire, lovely history lesson, but what's the point?" asked Emma from Bath, a client who'd spent twenty minutes staring at her chart trying to work out why her Venus felt so... off.
The point is texture. Nuance. Specificity.
"A decan refers to a subdivision of a zodiac sign used to give a richer context to each of the signs' personalities and traits," explained astrologer Lauren Ash. "We assign planetary sub-rulers to the sign, and those sub-rulers give us additional layers of symbolism to apply to your birth date within your sign", added astrologer Rachel Lang.
Let's say your Venus sits at 12 degrees Virgo. Virgo is an Earth sign and the degree would fall in the second Decan which, when we follow the natural zodiac, brings us to Capricorn. Mercury rules Virgo and Capricorn is ruled by Saturn.
Suddenly that Venus makes more sense. That may explain why, if you have this Venus placement, when it comes to love you're more conservative and logical than most. In matters of money you might be an incredibly astute business person with this Venus placement!
The Real-World Difference
Someone with their Sun in the first decan of Aries? "If you are born within the first decan, or the first ten degrees (approximately ten days) of a sign, you embody your sign to the fullest", says Lang. Pure, undiluted Aries energy. Charging headfirst into things before checking if there's a wall in the way.
Second decan Aries, ruled by the Sun? The second, Leo decan of Aries with rays from the Sun pictures a very noble individual whose principles, aims and ambitions remain intact in the most trying circumstances. Still Aries, but with more dignity, more theatricality, and a dash of that Leo self-importance.
Third decan Aries, ruled by Jupiter? The third, Sagittarius decan of Aries with rays from Jupiter is a bold and brash one, that is more restless and eager to finish than even the first decan. Same fire, different kindling.
Decans in Predictive Work: When They Actually Shine
The decans and rulers are worth investigation and have proven effective in predictive astrology, especially in the progressed horoscope. This ain't just academic navel-gazing.
Medieval astrologers took this seriously. "The 4th century Sicilian astrologer, Firmicus Maternus, is among many who placed great emphasis on (the Decan's) use, saying that a planet in its own decan is as good as in its own sign".
That's high praise in a system where planetary dignity determined everything from marriage prospects to whether you'd survive a nasty cold.
The Magical Connection Nobody Expects
Here's where it gets properly weird. You may have heard the decans described as "faces" before. This goes back to the notion that Gods inhabit each decan. The God within the decan is using it as a "face" or "mask" that it can take shape from.
Every pip card in the Minor Arcana from Two through Ten? Linked to a specific decan. The Three of Wands? That's Mars in the second decan of Aries. The Five of Cups? Mars in the first decan of Scorpio. The Chaldean decans are also the system used in the tarot decan associations of Rosicrucian and founder of the Hermetic Order of the Golden Dawn Macgregor Mathers.
Which System Should You Use?
Honestly? Try both.
Traditional astrologers working with horary questions or medieval techniques tend to stick with the Chaldean order. It's what William Lilly used in the 17th century, and if it was good enough for him, it's good enough for them.
Modern psychological astrologers often prefer the triplicity system because it's more intuitive and easier to teach beginners. The elemental connections just make sense to contemporary minds.
Neither is "wrong." They're different lenses on the same phenomenon, like looking at a building from the front versus the side. You see different details, but it's still the same building.
Start Simple, Then Complicate
Don't try to master decans before you've got the basics down. Seriously. It's like trying to run before you can walk—you'll just face-plant and give up.
But once you're comfortable with sign placements, house positions, and major aspects? Then start looking at where your personal planets fall within their signs. "Approximately the first ten days of your sign is the first decan, approximately the second ten days of your sign is the second decan, and approximately the third ten days is the third decan", explains Ash.
Take it slow. Look at one planet at a time. Notice the subtle shifts in expression.
The Egyptian Legacy We've Half-Forgotten
It's easy to forget that all this started with Egyptian priests watching the night sky from temples along the Nile. After Hellenistic astrology arose in Alexandria, recorded principally in the work of Ptolemy and Vettius Valens, various systems attributing symbolic significance to decans arose and linked these to the classical planets.
That synthesis—Egyptian time-keeping meeting Greek philosophy meeting Mesopotamian planetary worship—created something that's lasted more than two thousand years. Not bad for a system originally painted on the inside of coffin lids.
After the conquests of Alexander the Great which started in 334 BC, and as Egypt became Hellenized, the 36 decans were synthesized with the system of 12 zodiac signs. Different cultures, different gods, different priorities—all melting together into what we now call Western astrology.
Practical Application: A Real Example
Let's get concrete. Say you're looking at someone's chart and their Mercury sits at 25 degrees Leo. That's the third decan of Leo.
Using the triplicity system, the third decan of Leo is ruled by Sagittarius' ruler, Jupiter. This Mercury thinks big, possibly too big. Grand ideas, sweeping statements, the kind of person who turns a story about buying milk into an epic narrative about the human condition.
Using the Chaldean order, that same degree is ruled by Mars. This Mercury's got an edge to it—sharper, more combative, quicker to argue a point. Still expansive, but with more heat.
Same planet, same degree, different flavours depending on which system you apply. Both give you useful information. Both add depth.
Don't Get Lost in the Weeds
That's the key word: sometimes.
If you're spending more time calculating decan rulers than actually interpreting the chart, you've missed the point. The decans are seasoning, not the main course. A good chart reading doesn't depend on them, but a great one might include them where relevant.
Think of it like cooking. You don't need to understand the molecular structure of salt to make decent food. But knowing when and how much to add? That's what separates the amateurs from the pros.
The Modern Revival
For decades in the mid-20th century, decans fell out of fashion. Too complicated, too medieval, too much faff. Then traditional astrology had its renaissance, and suddenly people were dusting off old texts and rediscovering techniques their astrology teachers never mentioned.
Austin Coppock's book "The 36 Faces" came out in 2014 and gave contemporary astrologers a comprehensive look at the decans' history and application. Diana K Rosenberg did similar work connecting decans to fixed stars.
Now you'll find decan information on most astrology websites, often with detailed personality descriptions for each 10-degree segment. Whether that's progress or just information overload depends on your perspective.
When Decans Actually Matter
In natal work, they add texture. In progressed charts, they can indicate timing and thematic shifts. In horary, they were considered minor dignity that could tip the balance in a close call.
But honestly? Most of the time, you won't need them.
It's when you hit those moments—when a chart almost makes sense but something's slightly off, when the standard interpretation doesn't quite fit—that's when you dig deeper. That's when you start looking at the decan rulers and suddenly everything clicks into place.
"Oh, that's why her Gemini Sun feels so earthy. She's in the Virgo decan."
"Right, that explains the Mars energy in his Libra Venus. Third decan."
Those little revelations? Worth the effort of learning the system.
Moving Forward
The decans give a bit more flavour or character to the zodiac signs. That's all they do, but sometimes that's exactly what you need.
Don't feel pressured to become an expert overnight. Play with them. Look up your own planets' decan placements. See if the descriptions resonate. Try both systems and see which one speaks to you.
Astrology's a big tent. There's room for minimalists who stick to the basics and maximalists who want every possible layer of detail. The decans are there if you want them, quietly adding depth to the picture, linking us back to Egyptian priests watching stars rise over the Nile thousands of years ago.
Not bad for a "minor dignity", eh?
