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True Sidereal Astrology and Different Zodiac Systems

Updated: May 8

True Sidereal Astrology uses one of several Zodiac systems and approaches in Astrology. It’s the only system that is based on the actual sky and our alignment with the constellations.

I recommend you read this blog along with How Your Natal Chart is Calculated and Understanding Your Sun, Moon, and Ascendant Signs to get the most comprehensive understanding of this cosmic information!

What is True Sidereal Astrology?

Just like any profession, Astrology has branches, facets, and different approaches. The Zodiac calendar is not the only variation found in this modality; the House system and even the overall chart construction can be approached in various ways. It all depends on the Astrologer you’re consulting or learning from. Each system has a reason and purpose behind it. This is why you may get different charts when using different online chart calculators! Don’t fret; just because you have two different charts doesn’t mean that one is “wrong;” it just means there are multiple ways of interpreting the information present. My blog about How Your Natal Chart is Calculated is an excellent resource to read in addition to this blog post.

Though I personally use multiple approaches to understanding my chart, I professionally prioritize the True Sidereal Zodiac because of the different perspective and depth it has offered me. Here's a short video to go along with this written content!

There are three main Zodiac systems used in Astrology these days: The Tropical Zodiac, used by mainstream or Western Astrology; the Sidereal Zodiac, used by Vedic Astrology; and the True Sidereal Zodiac, used by Astronomical or Constellation-based Astrology. We will take a quick look at each, but first, let’s briefly discuss what the Zodiac even is.

What is the Zodiac?

Natal chart showing Zodiac and House system

A brief definition of the Zodiac or Zodiacal belt is that it is the backdrop and energy cycle behind the ecliptic plane in our Solar System (shown below). When looking at your natal chart, the Zodiac is the outermost ring consisting of the Zodiac signs we are all so familiar with, like Aries, Taurus, and Gemini. What is the ecliptic plane? This is the path that the celestial bodies orbit around the Sun. It’s an electromagnetic plane of energy that once captured the physical matter in orbit that we now know as planets, asteroids, and more.

Behind this ecliptic plane lies the Zodiac, which shifts depending on the approach used to calculate it. This will make more sense as you continue reading!

For the purpose of this blog, we are only looking at and discussing the very outer ring of the chart, the backdrop of all of your chart placements. From Aries to Pisces, this cycle of energy infuses your various chart components with a specific expression associated with the Zodiac sign they align with.

Ecliptic plane diagram of Solar System with Zodiac constellations

The Tropical Zodiac

By far, the most well-known and commonly used Zodiac system is the Tropical Zodiac. Used by the majority of Astrologers in the United States, this is the system with the dates that we are all familiar with. Born between March 21st and April 19th? You have an Aries Sun sign, at least according to this system.

The Tropical Zodiac consists of 12 Zodiac signs, each getting an even 30º slice of the 360º Zodiac wheel. As we make our annual orbit around the Sun, the Sun spends about a month in each of the 12 signs. This system is calculated by the seasons on Earth, not the constellations. That is the main difference between this system and the others.

When using the Tropical Zodiac, the first day of spring or spring equinox (the day in March when we experience 12 equal hours of night and day) always marks 1º Aries. So, the first day of spring always kicks off the Aries season. The first day of Summer, or summer solstice (the longest day of the year), marks 1º Cancer. Cancer season kicks off the Summer season. The first day of Fall, or the fall equinox (the day in September when we experience 12 equal hours of night and day), always marks 1º Libra, so Libra kicks off the Fall. On the first day of Winter, the winter solstice (the longest night of the year) marks 1º Capricorn. Capricorn greets the winter season. And then the cycle starts all over again with the following spring equinox kicking off Aries once again. It’s a consistent system that never changes.

The Tropical Zodiac runs on a cycle of time created by the tilt of the Earth’s axis in relation to the ecliptic plane. Because our axis isn’t parallel with this plane, we experience chapters of longer days and longer nights each year, with the equinoxes and solstices marking changing points in the seasons.

What most don’t realize is that just because the Tropical Zodiac categorizes the Sun in Aries or Gemini or Scorpio doesn’t mean that’s where it’s actually located by constellation. In fact, the Tropical Zodiac isn’t based on constellations as we align with them in our sky today. As soon as you start wanting to know where the Sun and other celestial bodies actually were in the sky by constellation at a specific time, you are headed into the territory of the Sidereal and True Sidereal Zodiac.

Sidereal and True Sidereal Zodiac

These two systems are similar, so we will discuss them together. The word sidereal means “of or with respect to the distant stars.” The Sidereal and True Sidereal approaches to the Zodiac are systems founded on our alignment to the constellations rather than the seasons. There are Astronomical rotations (the precession of the equinoxes) in our solar system that cause our alignment with the constellations to be ever-changing, meaning that as we make annual orbit around the Sun, we don’t return to the same position and alignment with the constellations as we had when we started the orbit. Our cosmic position shifts ever so slightly year after year, meaning that the dates when the Sun is located in the Aries constellation also shift. It’s a system based on our placement in the Solar System at large, not on the seasonal time of year for us on Earth. The Tropical Zodiac does not consider this third rotation of the Earth (the precession of the equinoxes), but Sidereal and True Sidereal Astrology do.

So, let’s say you were born on March 30th, a solid Aries Sun Sign according to the Tropical Zodiac. Even though mainstream astrology would categorize you as having an Aries Sun, the Sun was technically still located in the constellation Pisces when you were born. So, Sidereal and True Sidereal Astrologers would categorize you as having a Pisces Sun sign. Confusing, right? How can you be an Aries and Pisces Sun? Stay with me…

The Sidereal and True Sidereal Zodiac are systems that honor our ever-changing alignment with the constellations and interpret chart components based on our alignment with the stars, not the seasons. The Sun is still in the Pisces constellation when the first day of spring arrives, so Sidereal and True Sidereal Astrologers would interpret it as such. In another several thousand years, the first day of spring will align in the Aquarius constellation. These two systems will continue calculating the Zodiac according to our positioning with the stars, not the season. Right now, there is about a whole sign difference between the Tropical and Sidereal/True Sidereal Zodiac systems.

The only difference between the Sidereal Zodiac used by Vedic Astrologers and the True Sidereal Zodiac used by Constellation-based Astrologers is the number and size of the constellations used in the calendar. The Sidereal Zodiac uses the same 12 Zodiac signs as the Tropical Zodiac, and each still gets an even 30º slice of the 360º chart. The True Sidereal Zodiac uses 13 Zodiac signs (some Astrologers even use more, like Cetus) and is a calendar that honors the actual sizes of the constellations in our sky.

It’s a nice thought to think that each Zodiac constellation takes up the same amount of space along the ecliptic plane (12 signs of 30º each to form a 360º circle), but that is not the case in physical reality. Virgo takes up 44º of the Zodiac calendar and is the 2nd largest of 88 total constellations in our Solar System, while Cancer takes up less than 23º. The Sun (and all other celestial bodies) spend much more time in the Virgo constellation than in the Cancer constellation. When you look at a True Sidereal Zodiac calendar, you see that there are different sizes for each of the Zodiac constellations, including the 13 Zodiac sign, Ophiuchus, recognized by NASA as being part of the ecliptic path that we orbit along.

The True Sidereal Zodiac is the only calendar system based on astronomy that accurately reflects the constellations and our alignment with them as we know them today.

Diagram of Three Zodiac Systems

The History of the Systems

Diving into the history of these systems really allowed me to connect to the purpose of each of them. There is no right or wrong system. I repeat, there is no right or wrong system! Our ancestors were much more tuned into our connection to the sky than we are today, and we’ve always known that our alignment with the constellations is ever-shifting. The Sidereal Zodiac and Vedic Astrology predate the Tropical Zodiac. About 2,000 years ago in ancient Babylon, an Astronomer, Ptolemy, formally made the Tropical Zodiac the standard approach because it was more valuable at the time to track the seasons for the purpose of agriculture. Having a consistent system based on the seasons, as well as pairing nicely with the months of the year in the calendar (12 equal signs, each claiming one month of the year in terms of our orbit around the Sun), made life easier rather than going off our ever-shifting alignment with the constellations. Here's a great history paper with more details.

The history and use of the True Sidereal Zodiac system get a little more complex. The True Sidereal Zodiac, as described above, is unique because it honors the different sizes of the constellations as we know them in our sky today and includes Ophiuchus. The boundaries of the constellations in our sky have evolved over the thousands of years of human civilization.

Think about it: historically, no culture or region had the same understanding of the sky, especially before we could communicate with each other. Each and every culture had its own mapping of the sky and constellations before we created a universally accepted map. There are many different kinds of Astrology out there that I haven't even discussed here! Mayan and Chinese Astrology are two systems that are pretty different from the system we've explored here. What I find super interesting is that evidence of some sort of star-based practice has been found all around the world in all kinds of cultures from the very beginnings of our history. Exploring our human experience through the stars above is part of our DNA, and Astrology is the ancient language of the stars.

So, what the Greeks called the constellation Virgo back in the day was a cluster of something entirely different to Native American tribes and something entirely different to Aztec and Mayan cultures. Over the thousands of years of global centralization, we’ve created a universal understanding and map of all the stars in our Solar System. There are actually 88 total constellations in our Solar System. Your natal chart only includes the 12+ that are part of the Zodiacal belt behind the ecliptic plane. Those are the stars that so curiously captured the attention of our ancestors, as they were the stars that interacted as the backdrop with the planetary bodies.

It wasn’t until 1930, when the IAU (International Astronomical Union) formally published new boundaries initially proposed in 1928 for the constellations, that Ophiuchus became a recognized constellation of the ecliptic by NASA, meaning that the Sun and other celestial bodies spend a portion of time in alignment with Ophiuchus each year as the Earth orbits the Sun, according to these new boundaries.

What’s super fascinating and relevant to me as an Astrologer is that PLUTO WAS ALSO DISCOVERED IN 1930! There is a definite correlation here between Pluto's discovery, Ophiuchus joining the ecliptic, and the True Sidereal Zodiac resulting, which reflects the purpose that this Zodiac calendar has. If I had to boil it down to what I know of this system, the True Sidereal Zodiac is a shadow Zodiac designed to take you more into the dynamics of your discord, darkness, and wounding. It reveals more of what’s happening beneath your Tropical Chart's harmonious surface. Another way to say it is I've noticed the Tropical Zodiac as being more in tune with our Ego dynamics, while the True Sidereal Zodiac is more Subsconscious dynamics. Blog post coming on this soon...once I have it written, it will be linked here!

This is a relatively new and emerging system based on modern-day Astronomy. Very few Astrologers practice and teach this system. Some Astrologers are against it. It’s a controversial topic in the field right now. It is expected, reasonable, and natural for professionals to create new avenues to develop the work they are mastering. Diversity in Astrology is a good thing, just like having a variety of Doctors out there with specialties and specific skills. It keeps us open and curious to new ways of looking at things, allowing us to evolve in the practice. I encourage collaboration over competition when it comes to other Astrologers sharing their thoughts and insights.

What’s most essential for you on the consumer side of this industry is how you resonate with the Astrologer you are working with. Do they make sense to you? Do they bring clarity over confusion? Do you feel a heart tug to go deeper with them? I always recommend visiting the work of multiple Astrologers because it will support your comprehensive understanding of this modality.

Photons and Quantum Connection

Animated Flower of Life

I use the True Sidereal Zodiac because I have connected to this modality through quantum physics and verifiable facts. It feels misaligned at my core to say that Venus was in Cancer when you were born when it was actually interacting with and reflecting the photons from the Gemini constellation. We are all very unique light patterns manifested in the physical on the densest planet in our solar system, Earth. Your unique light pattern is in your energy field. It is founded on the dynamics of your natal chart, showing exactly how all the photons and other quantum particles were moving in relation to each other when you took your first breath as an individual human in this life, including the other stars in our Solar System. This is why I personally and professionally use the True Sidereal Zodiac the most and find validity in the information it reveals.

So, You Have Different Signs Between Systems…

Are you having an identity crisis over your signs changing? I did, too. One of the most significant shifts in my chart between the Tropical Zodiac to True Sidereal Zodiac is my moon sign moved from Virgo to Leo. It blew my mind and made me question everything, which almost made me abandon the practice of Astrology forever. Now, I try to help other Astrology students avoid this chapter of confusion by helping them understand why you can have the moon, Sun, or any other celestial body in two different signs and still get to know who you are. In fact, this additional information allows you to go deeper into your knowingness of who you are.

Let me ask you something. How many ways are there to look at God? Like infinity, right? This is the principle we are working with when looking at two charts with different information. Different charts are just different mirrors for looking at yourself.

You are a reflection of the entire Solar System, a beautiful fractal expression of all the Zodiac signs, all the houses, and all the celestial bodies vibrating with a unique frequency. You are not just your Sun, Moon, and Ascendant signs. We all have a connection to Aries, Saturn, and the 3rd House; it's just the nature of your connection that changes when you use a different Zodiac system. Your natal chart is incredibly nuanced because there is only one you in this world. When I moved to the True Sidereal Zodiac and my moon sign changed from Virgo to Leo, this wasn't communicating that I no longer had a connection to Virgo; this communicated that my relationship with Virgo changed. It allowed me to see my Virgo energy in a new way. That's all.

Why would a single chart show all of who you are? Aren’t there layers and facets to you? Aren't there always new things to learn about yourself? One of the most significant mishaps I see in Astrology is that we like to identify with our charts. I am a Pisces Sun, Leo Moon, Ascendant in Virgo, but is this who I am? No! I am the conscious awareness experiencing this Pisces Sun, Leo Moon, Ascendant in Virgo energy dynamic.

When my chart changed when I calculated it through the True Sidereal system, the change in signs had nothing to do with my identity. The new information offered me an alternative perspective on understanding my human experience and the dynamics of my energy field. What’s important to note is that the ONLY thing that changes when you try a different Zodiacal system are the signs that your chart components are in. It doesn’t change the house position or the aspect relationships between the planets. In other words, if Mercury were squaring Mars in the Solar System when you were born (known as a square aspect), that would remain constant in any system. The planetary positioning of the Solar System doesn’t shift. The only thing that shifts is the Zodiac sign they are associated with.

Black and White vs. Shades of Gray

When you really think about it…isn’t it weird that we have boundaries marking energetic sections of our sky? Like Aries marks an energetic time of self-prioritization, just going for it and taking instinctual action. The Tropical Zodiac draws the Aries boundaries one way, and the True Sidereal Zodiac draws them another. This comes back to what the Zodiac even is: a cycle of energy. From Aries to Pisces, from separation back to unity, the Zodiac is a spectrum, and each degree of the 360º circle contains its own energy. 5º Cancer is a different energy than 20º Cancer.

So maybe we can broaden our understanding of the Zodiac into something more than a black-and-white system with fixed borders. This is why I and other Astrologers read cusps—when a chart component is located between two Zodiac signs. There is an evolution of energy that takes place as we cross the boundary from one sign to the next.

Does a kitten just one day become a cat? Does spring suddenly become summer overnight? No. Our world shows us evidence of gradual shifts and changes. I see the cycle of the Zodiac the same. We don’t move from Aries straight to Taurus. There’s an evolution of Aries energy as any chart placement moves through the sign and slowly becomes Taurus energy, which then evolves to Gemini energy.

I share this perspective of the Zodiac with you because when you understand the cycle of energy that the Zodiac is, you don’t get so caught up on arbitrary boundaries that change between systems. The Tropical Zodiac draws the boundaries like it does because Western Astrologers connect more to the significance of the seasons in our human lives. The True Sidereal Zodiac draws the boundaries like it does because Constellation-based Astrologers connect more to constellations.

Your identity doesn’t change just because the Zodiac does. The different Zodiacal systems allow alternative perspectives on your human experience and energy dynamics. You may resonate with multiple perspectives, which means you are a multifaceted and layered Soul. Let yourself be just that!

How Does the True Sidereal Zodiac Change Your Chart?

Are you curious about how your chart changes using the True Sidereal Zodiac? You can use my free online chart calculator to calculate your natal chart using the True Sidereal method. Interpreting and understanding your chart through different Zodiacal systems is a more advanced level of Astrology knowledge. I highly recommend you seek the assistance of a professional to help you understand the layers.

I offer two options for diving deeper into this topic with me as your cosmic guide. For $40, I offer 20-minute personal recordings analyzing the most significant differences in your chart between the Tropical Zodiac and True Sidereal Zodiac, focusing primarily on changes to your Sun, Moon, and Ascendant shifts.

For more profound work and insight, you can book a private 60-minute session with me for $110. I provide you with professional charts in the different systems to keep and use in the future. All sessions include a full transcript, video recording, and resources to apply the information we explore to your life for growth, healing, and Soul alignment.

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