Introduction to Technical Topics

The Sidereal vs Tropical Zodiac


Synetic Vernal Point

Great Ages of Astrology

by Margaret Penner Choinski


The astrological model postulates two zodiacs, the Sidereal and the Tropical. How did we happen to come up with two different zodiacs? What do they each mean at a personal level?

What is Precession, and what causes it?

What is the Synetic Vernal Point (S.V.P.)?

What Great Age are we in now, and when does it end?

“Observe due measure, for right timing is in all things the most important.”

-         Hesiod[1]


A long, long time ago, astrologers kept nightly watch on the stars. They dedicated themselves to recording their observances, making note of even almost imperceptible changes. As the decades, then the centuries passed, they realized that just as the Earth had Her seasons, so did the Heavens. That is, every year on the first day of Spring, the Sun was rising a little more west in the constellation. Over time, it was moving out of one constellation and into another! This process is called the Precession of the Equinoxes, and by its very existence it causes untold contention amongst astrologers. It is also a natural cosmic cycle, one that has been used with great derision against astrologers by scientists who have studied only its factual information.


     The point when once more day and night are equal after the Northern Winter is called the Vernal Equinox. The arrival of the Sun at this point has since ages past, heralded Spring. Any place lying along the Tropic of Cancer, a line of longitude 23.5 degrees above the equator, experiences the Sun directly overhead at mid-day.

THE CONSTELLATIONS...what about that 13th sign?

   At the Vernal Equinox, the Sun rises within a certain constellation. We in the West take this constellation to be Aries, but things are not as they seem. Once upon a time Aries did rise with the Sun on this day. But that has not happened for a very long time. The Sun began to rise in Pisces around 100 B.C., or at least was aligned with the first star of the constellation of Pisces at that time. Since each constellation is of different length, the amount of time it takes for the Sun to make its way backwards through each constellation is going to vary.

These constellations were called the morphomata, “that which has form,”
[2] and are the rough equivalents to our modern astrological constellations. The zodia noeta is the “knowable zodiac,” the twelve 30-degree signs that makes up the Sidereal zodiac.[3] The morphomata are the heavenly pictures of ancient imagination, and the sidereal zodiac roughly corresponds to those constellations we call signs. In the sky there are hundreds of constellations, but on our ecliptic are only 13[4] constellations that intersect the path of the planets, and twelve of those are the signs which astrology has been founded on.  

      Above the Earth and describing an arc 16 degrees wide, is the ecliptic. The ecliptic is not only a band of stars, but also the zodiac of astrology. Running counter-clockwise along this band is the measuring out of degrees, called Celestial Longitude. The beginning of the zodiac is at 0 degrees Aries, and it is in reference to that point that the planets’ position is calculated. The area above or below the ecliptic is also measurable by degrees and it is called Celestial Latitude. The stars ‘behind’ the zodiac are the Fixed Stars, called thusly for their apparent unchanging disposition. And they do not move, in reference to each other, but they certainly have shifted through time when compared to the changing position of the Sun on the first day of the Northern Spring.


Precession is caused by a physical movement of the Earth.

The polar axis running through both ends of the Earth is tilted at an angle, making a 90-degree arc from pole to equator. The equator is then at an angle of 23.5 degrees relative to the ecliptic. Because the Earth has this tilt where it is sometimes closer to the Sun and sometimes as far as it can get, we experience the four seasons. The polar axis, still spinning from the force placed upon the planet when Earth was first created, describes an imaginary circle above. As the axis moves, the orientation of due North also moves. And as it moves, it “points” to the sky, moving very slowly. Right now, our North Star is Polaris. Thirteen thousand years from now our North Star will be Vega. In 21,600 A.D. it will be Thuban, the Dragon Star.

This is the star which was said to be the Pole Star at the time when the Great Pyramid of Giza was built, with its Descending Passage oriented in such as way as to allow the Dragon Star to shine directly in: “the most precise alignment of the Dragon Star and the Great Pyramid occurred on the Vernal Equinox of the year 2141 BC.”
[5] In 27,900 A.D. the North polar axis will again be pointing at Polaris. This completion of a polar axis circle, is called the Great Year, and takes approximately 26,000 years. This is Precession on the largest scale. Now there is another factor to consider: our Sun and our Moon exert a gravitational “pull” on the Earth. This causes a little “wobble” in the movement of the polar axis. I should say “little” wobble, because anything little on an astronomical scale is, well, astronomical!

     The wobble causes the axis to describe a tiny circle of 71.5 years (or 1 degree backwards along the ecliptic), within the large circle of the Great Year. Therefore, the Vernal Equinox point moves 1 degree back through a fixed star constellation, taking approximately 2100 years to complete. This is an approximate length of time because of the variance in each constellation’s size---Scorpio is about 7 degrees, while Virgo is over 44 degrees long. This is the observable phenomenon of Precession, where a civilization such as ancient Babylonia would have had sufficient time to discover the changing of the signs on the vernal point.

Hipparchus, a Greek astronomer of the 2nd century B.C., is credited with the official discovery of Precession. At that time, the vernal point would have been just about to change from Aries, to Pisces. However, it seems to me that since our tropical zodiac is set at 0 degrees Aries as its start, then sometime during the time the vernal point was in Aries the decision was made to mark the beginning of the Northern Spring in this sign, for good.


     As there is a Great Year, so there are 12 Great Months of this Year, and each month is called an Age. Each Age is generally thought to be about 2100 years long, although of course each Age would be as long as its constellation. Currently, the vernal point is at 5 degrees of Pisces and so we are in the Age of Pisces. Presumably, the Age of Aquarius looms, not only because everyone says so, but also we are near the end (beginning) of Pisces. Five degrees x approximately 72 years = 360 years hence, i.e. 2366 A.D. This is one date for its birth. Carl Jung favoured 1961; Bessie Leo put it at March 1928, whilst Adrian Duncan points to the Grand Mutation of Jupiter and Saturn in Aquarius in 2020 as a likely starting point.< /FONT > [6]

Robert Hand has an intriguing way of choosing his date: he has plotted the conjunctions of the vernal point with the fixed stars through the constellation of Pisces. He cites the conjunction with the last fixed star in Pisces, around 2800 A.D., as the end of the Piscean Age. Based on this he begins the Pisces Age at the conjunction of the vernal point with the first fixed star of Pisces, around 100 B.C.


     At one time the Sidereal and the Tropical zodiac began at the same point. Hand puts this agreement at 221 A.D. [8] At the time Ptolemy wrote his Tetrabiblos the two zodiacs roughly matched, and so although he made no distinction between the two at the time, it caused little trouble. As the years went by, however, the gulf between the each system’s vernal points became noticeable. Now it has reached a distance of approximately 25 degrees, and hence, causing a great many people to wonder what in the world is going on with astrology.

     The difference between the two zodiacs is not one truly of numbers however, but of perspective. When the Tropical zodiac was set in its 12 equal sections, based on the recognizable constellations of the ecliptic, the vernal point was in Aries. As there were four seasons, there were four main sections of the zodiac relating to each season as it came. Soon there were 12 months of the year, which went hand in hand with the 12 zodiac signs. The astrological year was nominated to start on or about March 21; at one time it really was 0 degrees of Aries up in the sky. Thus the signs related directly to the changes happening here on Earth, the place we are born, live, and die.

The subtle qualities of each season, with its connotations of fire, earth, air, and water, gave depth to each sign. The records of the Babylonians with their copious omen lore based on the weather and other events, all added to the knowledge of an earthly-focused astrology. Whether the stars wheedled around or stayed still, was of no concern. Tropical astrology was all about the here and now. Into this way of looking at how the signs colour the planets, we have incorporated the processes and movements of Nature into their characteristics. The Tropical zodiac brings the planets down to Earth. Thus, “You were born when the Warrior was trudging through a cold and barren, mountainous land,” becomes Mars in Capricorn. And we know it works, because it makes sense to our basic orientation.


     Sidereal astrology tied itself firmly to the stars. In fact, “sidereal” means, “star.” From the beginning the Sidereal zodiac was correlated, in terms of longitude along the ecliptic, with the constellations. The alignment was never exact. Because the Sidereal zodiac is of 12 30-degree segments, as is the Tropical zodiac, the alignment was “thereabouts.” However, Sidereal astrology has taken Precession into account and set its Vernal Equinox at the time the Sun aligns with a Fixed Star in the constellation of Aries. [9] But the exact beginning of the constellation of Aries is in dispute.

This has caused some problems for the Siderealists in calculating the beginning of their zodiac. The difference between the 1st degree of Aries in the Tropical zodiac and the 1st degree of Aries in the Sidereal zodiac is called the ayanamsa, a calculation based on Precession, the position of the Tropical zodiac, and the year in which both zodiacs were aligned. Since this calculation is critical to the proper practice of Sidereal (Hindu, Vedic, or Jyotish) astrology, the Indian government sanctioned the ayanamsa of N.C. Lahiri as being the official numbers that should be used.
[10] What a difference this attitude is to the derision heaped upon Western astrologers and their “illogical” art.

     And it doesn’t stop there. The Siderealists attack the Tropical astrologers for a similar reason. But the Sidereal zodiac and its long tradition of interpretation come from a culture that has attempted to internalize the infinite into the everyday. From the Indian perspective, it was the big things which mattered, written large in the night sky. Sidereal astrology is oriented toward events, toward what happens Out There and how it impacts the person. This is almost the antithesis of the Western Tropical approach, which is centred on the complexity of the human being and how each person affects his or her external surroundings. James Braha comments: “…many New Agers and disciples of spiritual movements these days consider anything Eastern to be deep, pure, and profound, and anything Western to be shallow, superficial, and tainted. Where astrology is concerned, this is a very sad mistake.” [11]

The truth is, both assume a psychology that comes from a certain orientation. In Western astrology, we think, “That which is in me is out there.” In Sidereal astrology, we think, “That which is out there is in me.” It is a subtle yet profound difference and one that makes all the difference when it comes time to read a chart.

The immense, awesome, Nature of the stars is reflected in the philosophy of the Eastern follower of astrology: “Ultimately, nothing becomes impossible because the results of one’s actions are forever creating a new destiny, even while one paradoxically experiences one’s current fate in the form of circumstances to be modified.”
[12] Contrast this to the adherent of the Tropical zodiac, where the world holds the secrets to our inner workings. The question as to which zodiac is more scientific, more spiritual, or even more accurate, is absolutely irrelevant. A person speaks best the language they learned first. The zodiac is like a universal language of truth. And as Krishnamurti declared, “truth is a pathless land.”[13]




Braha, James, and de Fouw, Hart, Eastern Systems for Western Astrologers, An Anthology, Samuel Weiser, 1997

Hand, Robert, Essays on Astrology, Whitford Press, 1982

Hand, Robert, Horoscope Symbols, Schiffer Publishing, 1981

Spencer, Neil, true as the stars above, Victor Gollancz, 2000

Internet articles:

http:// Jim A. Cornwell

The following two internet articles were remarkably helpful: Nicky Anthony Fiorenza Dwight Ennis

Copyright: Margaret Penner Choinski

                  Earth Elephant Astrology


[1] Greek Didactic poet, author of “Works and Days” and “Theogony;” lived about 800 B.C.

[2] Hand, Robert, Essays on Astrology, Whitford Press, 1982, p.147

[3] ibid

[4] The so-called 13th sign of the zodiac, Ophicuchus, a constellation that intersects the ecliptic between Scorpio and Sagittarius.

[6] Spencer, Neil, true as the stars above, Victor Gollancz, 2000, pgs.122-126

[7] Hand, p.152

[8] ibid

[10] Braha, James, Eastern Systems for Western Astrologers, An Anthology, Samuel Weiser, 1997 p.275

[11] ibid, p.273

[12] de Fouw, Hart, Eastern Systems for Western Astrologers, An Anthology, Samuel Weiser, 1997, p.221

[13] Spencer, p.125

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