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What is Western Sidereal


​Sidereal astrology, from the Latin sidus, (star) or sidereus, (starry), is the type of astrology that reckons celestial longitude from the positions of the stars rather than the vernal equinox. Western sidereal astrology is based on the Babylonian sidereal zodiac, the original zodiac. Western sidereal astrology is both new in the West and the revival of an ancient art. Babylonian astrology was introduced to the West in 1944 by Cyril Fagan, an Irish astrological scholar, after he had studied the translations of the ancient Babylonian astronomical and astrological texts excavated from the Near and Middle East.

Frequently Asked Questions
Who Discovered the Zodiac?

It was the Babylonians ​who, through centuries of observation, refined the zodiac, the central pillar of astrology. ​The zodiac is an exclusively Babylonian device later adopted by the rest of the world. There is no hard evidence extant that any culture has a body of zodiacal lore older than the Babylonian material. By mid-first millennium B.C., after many centuries of documented observation, the Babylonians constructed mathematical models of planetary motion that led, in the fourth century B.C., to the first ephemerides. This development wasn’t duplicated until the Greeks adapted Babylonian methods to their own scheme in the second century B.C. The earliest record of astrological advice given to a Babylonian king is from 709 B.C. The earliest eclipse record available to Hipparchus, the likely inventor of the tropical zodiac (whose last works are from 127 B.C.) was from the first regnal year of the Babylonian king Nabonasser, 747 B.C.

How Did Western Sidereal Astrology Come to the West?

This is explained in great detail in Appendix One of my book, An Introduction to Western Sidereal Astrology. In a nutshell, when the Near and Middle East were excavated during the 19th century, scholars discovered that almost all of the astronomical material found there was sidereal. By the 1870’s, after Akkadian, the language of ancient Babylon, had been deciphered to a significant extent, this material was published in a variety of academic journals. In the mid 20th century, an Irish astrological scholar by the name of Cyril Fagan discovered this material. After many years of private study, Fagan, a long-time tropicalist, was forced to conclude that astrology was originally sidereal in the ancient world until the Greeks began to use the equinoxes and solstices to reckon celestial positions, probably around the time of Hipparchus of Rhodes. Fagan is often called the “father of western sidereal astrology.” He wrote a monthly column on the subject in American Astrology Magazine from 1953 until his death in 1970 that influenced a new generation of astrologers. He also wrote several books on the topic including Astrological Origins, Zodiacs Old and New and Symbolism of the Constellations.

How Can I Find Out More About Cyril Fagan's Work?

A brief biography of Cyril Fagan is available on this site. We have recently secured the rights to Fagan's articles from American Astrology Magazine. We will publish these articles in a series of books and also post selected articles on this site. Fagan's second book, Symbolism of the Constellations is out of print but can be found via a web search. Astrological Origins can be ordered on We will publish a new edition of his first and best known book, Zodiacs Old and New, in 2022. If you would like to be notified when the books become available, please join our mailing list.

​What is the Difference Between Tropical and Sidereal Astrology?

In the sidereal system the positions of celestial bodies are reckoned from the stars—it's a fixed stellar frame of reference. In the tropical system, the positions of celestial bodies are reckoned from the equinoxes and solstices—it's a seasonal frame of reference. The tropical zodiac is known as the "moving zodiac" because the equinox is constantly drifting westward against the background of the stars. The tropical zodiac moves with respect to the stars because it doesn't take into account one of the earth's orbital motions: precession. Precession can be illustrated by looking down at a child's spinning top. The top has a secondary motion inside its spin—it wobbles or precesses about its spin axis—just as the earth's pole describes a complete circle with a radius of 23 and 1/2 degrees in 25,800 years. This means the equinoxes continuously point at different stars over time—not the same star year after year—on the days of the equinoxes. The rate of change between the equinox and the sky is approximately 50.25 seconds of arc per year or about one degree every 71 and 2/3 years. The term "tropical" refers to the tropics of Cancer and Capricorn that describe the limits of the Sun's maximum declination values north and south of the equator. The Sun's declination is zero at the spring and autumnal equinoxes when day and night are equal. Sidereal astrology employs declination to describe positions of bodies but not to define the limits of the zodiac.

How Does the Actual Practice of Western Sidereal Differ from Tropical Astrology?

The main difference is, of course, the zodiac. Both tropicalists and western siderealists use primary directions, secondary and tertiary progressions, transits, astrocartography and other methods. There are two main points of departure: timing, and the problem of tropical versus sidereal sign meanings. In the first case, because tropical reckoning ignores precession, a timing error accrues with age that becomes an entire degree by age 72. The Sun takes about a day to advance a degree in the zodiac but Saturn can take more than a month to move a full degree. In the second case, the problem is legitimacy. The sidereal position is that trait characteristics derive from the archetypal and original zodiac: the zodiac of the stars. An archetype is invested with meaning because it is original and self-defining. It exists regardless of our awareness or beliefs. This issue addresses the matter of whether trait characteristics are carried by the sidereal signs or the tropical signs. In other words, which one is invested with legitimacy? They can't both be right. As the tropical signs precess farther and farther away from their sidereal namesakes, the most glaring issue between tropical and sidereal reckoning is thrown into bold relief. As the tropical and sidereal signs have slowly drifted apart, the tropical signs have become blurred by their overlap with the adjacent sidereal signs that carry the original sign characteristics. ​The meanings of the tropical signs have evolved to compensate for the problems of precession a​s the signs ​​have slowly moved out of the territory of ​​​the ​​constellations that was their original venue. For example, most of what is called Scorpio in terms of ​tropical zodiac reckoning is the constellation of Libra. Scorpio is aggressive, insistent, penetrating and intense. It is typically harsh, forceful, intolerant of opposition and will attempt to crush an opponent by any means. Libra is ruled by Venus. It has a tender, artistic, pleasure loving and gentle quality. Libra is clearly a lover—and not a fighter—like Scorpio. The result is that tropical Scorpio is assigned many of Libra’s qualities. It is seen as sensual and erotic. This sort of bleed-over has happened with all the signs. Sidereal astrology restores the crispness of the sign traits to their original venue which was usurped by the adoption of the tropical zodiac in the West. The sidereal position is that if someone has the Sun in tropical Scorpio but sidereal Libra, only the Libran traits are considered valid.

How Does Western Sidereal Astrology Differ from Vedic or Eastern Astrology?

Both use the sidereal zodiac but there the similarity ends. Vedic astrology has it own unique rules of interpretation. Indian astrologers place great emphasis on the houses, and use a different set of aspects than the western siderealists. They consider aspects by sign only. These are very wide and broad categories compared to the closer, more precise nature of the western sidereal system. In addition, the western siderealists use the outer planets—Uranus, Neptune and Pluto—unlike the majority of Indian astrologers.

Why Study Western Sidereal Astrology?

Sidereal astrology is the pure unadulterated form of the art. It is the nexus of signs, aspects, planets and houses without a philosophical, psychological or New Age overlay. Sidereal interpretations are clear, concise and succinct. In the ancient world, astrology and astronomy were combined. The western siderealist becomes familiar with the sky and coordinate systems, as well as the history of the art itself. Although western sidereal astrology is a bit more technical then tropical astrology, a strong math background is unnecessary. My interpretation course was released in 2021. Click here for more information.


© Kenneth Bowser, 2013-2024


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