The greatest, most long-standing debate within astrology concerns the use of the tropical versus sidereal zodiac.
All astrologers agree that the ecliptic around the earth through which the planets travel comprises 12 distinct celestial entities known as the signs. However, astrologers disagree vehemently about the exact placements of these signs, how to measure their placement, and where exactly on the ecliptic the sequence of signs begins.
The two greatest competing views are the tropical view, that the position of the zodiac is defined by the position of the sun at the vernal point or spring equinox; and the sidereal view, that the position of the zodiac is defined by the position of a particular fixed star known as an ayanamsha.
So vast is the chasm between these two positions that they have birthed entirely distinct, semi-unintelligible systems of horoscopic astrology and natal chart analysis. Indian astrologers developed Jyotish Astrology, and Greek and Egyptian astrologers developed Classical or Hellenistic astrology.
At the outset of horoscopic astrology in the 3rd or 2nd century BCE, there was no difference between the two zodiacs - the placement of the vernal point aligned with the placement of the fixed star used in India. However, due to the precession of the equinoxes, the placement of the fixed stars will slowly “slip” in the sky at a pace of 1 degree every 72 years. Now, after several thousand years, the difference is irreconcilable.
The tropical system that traditional astrologers like myself use often comes under fire for being less “real” since it isn’t based on something you can see. And the fact that the constellations don’t line up with the signs of the zodiac is often used in popular culture to lampoon astrologers, especially Western ones.
In this article, I want to address these criticisms head-on and explain the reasoning behind the Western tropical model. Like most things that Western astrologers do, we have a lot of reasoning behind it and it’s not being done by accident.
After that, I’ll examine the sidereal system in more detail, and clear up a lot of common misconceptions about how the sidereal zodiac is actually calculated, and that sidereal astrology isn’t based on the placements of the constellations any more than Western astrology is.
Finally, I’ll close by talking about these competing zodiacs and their relationship with each other. I do think they are compatible, and I want to show how.
Tropical System
Let’s start with an image of the world according to the ancient mind. Every scholar, astrologer, occultist, and magician from the time of Plato’s academy, through to the catholic universities of the Middle Ages and the Renaissances, from Arabia to Paris, thought that the universe looked something like this:
At the center of the universe is our Gaia, a sphere of water and earth. Surrounding us are a sphere of air and a sphere of aethereal fire, and following that are the seven spheres of the planets. At the edges of the universe is the sphere of the stars and constellations called the Heaven of the Firmament, and then the final, outermost sphere stands the Crystalline Heavens, which the ancient Egyptians said was made of lapis lazuli. Surrounding this entire cosmos is the Heart and Mind of the Creator-deity, known in Western esotericism as Atum, The One, or Nous.
This final sphere - the crystalline vault of the cosmos - forms a complete revolution around the Earth every single day, carrying the planets, sun, moon, and stars with it. For this reason, it’s also called the primum mobile or first moveable. The Sun rises in the east and sets in the west each day because it's being carried by the primum mobile. Images of star trails in the night sky capture the motion of the primum mobile.
The crystalline heaven, in the Western mind, is the abode of the signs of the zodiac, rather than the realm of the stars. Western astrologers start the zodiac with the vernal point - the point on this heaven that the Sun occupies at the spring equinox.
Western astrology assigns the signs to the crystalline heavens because the signs of the zodiac represent unchanging, immaterial ideals. They represent the realm of absolutes and divine consciousness - the divine spark that we each carry within us that transcends the waxings and wanings and the ebbs and flows of the material world. They are of the realm of spirit, not matter.
Likewise, of all the realms in the universe, the crystalline heaven is the sphere most closely associated with the realm of spirit. It is the furthestmost sphere from the earth and the closest to the seat of the Divine Progenitor of creation. So it makes the perfect homes for the signs.
In contrast, because the constellations and fixed stars are more material, and because they do move (albeit very slowly), they can't be the home of the realm of the unchanging, eternal ideals that the signs of the zodiac represent. The stars are more of the realm of matter relative to the crystalline heaven. There’s a difference in kind: the signs can’t live here any more than a 3D being can live on a 2D plane, or in this case 12 13th-dimensional Gods slumming it up in the 9th dimension of the fractal cosmos.
So it's not that the tropical zodiac is based on something less real or more abstract, we just don't root the signs of the zodiac in the constellations. It doesn’t make sense with our models of the cosmos.
In fact, in the mind of the Ancient Egyptian or Greek philosopher, the crystalline heaven above is more real because it doesn’t move. It’s less material, less impermanent, and physically stationed closest to the Divine Progenitor, who is the realest of the real.
Interestingly enough, there are even fragments of ancient source texts describing astrologers and magicians ascending into the heavens and seeing the signs of the zodiac inscribed on the crystalline heaven. It’s always been a deep part of the astrological-magical consciousness.
This, in a word, is the Western model: the signs reflect the realm of the ideals and spirit, and so they live in the plane of existence most clearly associated with that. I’m not saying it’s better than the sidereal system, I’m just saying that it has its own logic to it.
So the arguments levied against us that we somehow “don’t know” that the constellations moved are absurd - we astrologers never thought that the signs mapped onto the constellations in the first place. All these arguments do is betray the ignorance of the person making the accusation.
The Sidereal System
In contrast to the tropical model, the sidereal system used by Jyotish astrologers still relies on the stars. The Indian schools of astrology first started rooting the signs of the zodiac in the realm of the stars to accommodate the precession of the equinoxes. Rather than the vernal point, they use a particular star called an ayanamsha to start their zodiac.
At first glance, this model seems more intuitive because it still gives the signs some kind of link to the constellations that share their names. But it’s not the case, as many people assume, that the signs of the zodiac in the sidereal model are identical to or coextensive with the placements of the constellations. The signs are still idealized 30-degree divisions into 12 distinct entities.
In contrast to these idealized divisions, the constellations vary greatly. They have differences in size, sometimes overlap each other, or admit gaps between them for people to sneak things like Ophiucus in when you’re not looking.
In sum, the only way that Indian astrologers incorporate constellations is to start the beginning of their zodiac with the placement of a fixed star. Moreover, there's lots of disagreement about which star to choose - and the different ayanamshas can vary up to 9 degrees. Each Ayanamsha could, in a way, be its own unique zodiac.
No one - except for one fringe type of astrology that has no historical basis - uses the actual constellations. Instead, most astrologers incorporate the stars and constellations through conjunctions and parans that planets will make with stars. This way, we can still talk about the relationship between planets and the starry constellations.
Two zodiacs, two operating systems
My goal with the above is to show you the inherent logic that both system contains. I don’t want to claim definitively that one model is better, but clearly, I have my preferences for the Western system.
For one, the mythology, history, and symbolism behind the planets, deities, and signs are far more familiar to me as a Westerner. And in my mind, if you’re going to use abstract, 30-degree divisions of the sky, it makes sense to map them onto a division of the universe associated with abstractions and ideals.
That said, there are some techniques in Jyotish astrology that I greatly admire. They also have a strong tradition around prediction and making concrete delineations about people’s charts, instead of just relying on psychology. In many ways, Hellenistic astrology as I practice it has more in common with Jyotish astrology than it has with modern astrology in terms of scope, predictive focus, and interpretations of the planets, signs houses, and aspects.
I don’t believe that these two models are mutually exclusive. Instead, I view them as two separate operating systems for computers - like Windows or Mac. Each system has unique, effective techniques for interpretation that only work on its own platform. I love Dasha systems and Nakshatras, but they don’t work with a tropical chart. I love zodiacal releasing more than any other predictive technique, but it works very poorly with a sidereal chart.
Some astrologers have taken to using sidereal charts and tropical charts together in chart interpretation and using the corresponding techniques with each system in the analysis of the native’s life. This is the equivalent of running a ghost drive of a different OS on your computer so you can switch over to that OS whenever you need it for a specific task.
To me, this kind of approach to me is the real way to reconcile these two systems. If you want the best of both worlds, use sidereal and tropical systems alongside each other in your chart analysis.
This approach sidesteps the question of which system is better. I think that’s a bad question - they each have unique interpretations they can offer based on techniques that only work with their zodiac model. It also bridges these together in a practical way, instead of claiming that one system describes the soul and the other the spirit, or other such unhelpful meaninglessness.
If you are just getting into astrology and deliberating between these two models, I hope this analysis of each system helps you to decide one on. If you have already landed somewhere, then I hope that this helps you to understand the reasoning and cosmology that informs the astrology you practice.
So the next time someone tries to make fun of you for not “realizing” that the signs and constellations don’t line up, just let them know who the real fool is :)