What is sidereal astrology: Everything to know about the alternative zodiac

What is sidereal astrology: Everything to know about the alternative zodiac


Reda Wigle

May 24, 2022 

Sidereel astrology wheen
Sidereal astrology bases horoscopes on the current position of the constellations.


Get ready for your horoscope to change it’s scope.

For centuries, human beings have searched the stars to help them navigate the earth and understand themselves. Ancient Babylonians were among the first to record the constellations along the ecliptic, the path the sun appears to make through the sky. 

These OG astrologers recognized that different constellations would rise from the horizon line at sundown during different times of year.

Back to the future

The Babylonians, who already had a 12 month calendar based on the phases of the moon, assigned a constellation to each month. They applied myths, based on earlier Sumerian beliefs to these constellations and thus the zodiac wheel was born. Scholarship is divisive but it is generally understood that Egyptians refined the zodiac, and the Greeks cast it into the form we recognize today. The Greeks also gave it a proper name, ‘zodiac’ is derived from the Greek for “circle of animals.” These oracle heeding, robe loving folk borrowed myths from earlier iterations and added some of their own gods and heroes for good measure. Later, the Romans in their eternal imperialism, replaced the Greek names with Latin.

Illustration of a Paying homage to an Assyrian ruler.
Babylonians were among the first to record the constellations that comprise the zodiac.


Illustration of the sun and moon.

Is your Zodiac sign a lie?: Vedic vs. Western astrology

Tropical vs. sidereal

Astrologers use two primary zodiac systems to divine meaning from the cosmos; sidereal and tropical. In both tropical and sidereal systems, the zodiac wheel is divided into twelve signs. The primary difference between the two systems is where those signs are placed in the sky. The sidereal system is based on the current position of the constellations while the tropical system is based on where the stars were around 0 AD. In essence, the dates of the sidereal zodiac change over time and the dates of the tropical zodiac do not.

There was a time when the two systems aligned but they diverged around the year 285 AD; coincidentally, this was also the year that the Roman empire split into two factions and began its fated decline. From that point, due to conquest and colonization, and as we’ll explore a bit later, aversion to math, tropical astrology became the predominant system in the Western world. Sidereal meanwhile remained, and remains the governing system of Vedic astrology. Read more about Vedic astrology here.

A blue illustration of the zodiac wheel.
Both tropical and sidereal astrology recognize the twelve signs of the zodiac.

Same wheel, two ways

We can thank the mathematician Ptolemy for the static positioning of the tropical zodiac. He suggested that the vernal equinox, and thus the start of the zodiac be set at 0 degrees of the Aries constellation each year to ensure continuity between zodiac signs and the progression of seasons in the Northern Hemisphere.

Sidereal astrology, by comparison, is a touch more technical. Just as time marches on, children age and cities fall, so to do stars shift. Sidereal astrology recognizes that the earth sits on a skewed axis that contributes to the ever changing distances between earth and the constellations above, a movement know as the procession of the equinoxes which sounds like but is in fact not, the title of a George R.R. Martin book.

Earth and solar system planets, sun and star. Sun, Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune, Pluto.
Both sidereal and tropical astrology divine meaning from the positioning of the celestial bodies at the time of birth.

The deal with sidereal

To account for this procession, sidereal employs a corrective system of equations or ayanamsas to more precisely determine the current position of each zodiac sign. Part of the reason the tropical system is predominant is because humans are lazy and math is hard. The most widely used of these equations is the Lahiri ayanamsa. Under this corrective, the Sidereal Zodiac recognizes an apparent backward movement of fixed stars of about 1 degree every 72 years. Meaning there is a 24 degree gap between the tropical and sidereal systems, making them roughly an entire zodiac sign apart.

Deep space background with nebulae.
For as long humans have been looking up, we have been fixated on the motion of the stars we find there.

Given the degree of discrepancy between tropical and sidereal systems, an individuals birth chart will vary according to which system is applied. While the dates of the respective zodiac signs are differ between systems, their qualities and influence are much the same. You can find your sidereal sign and birth chart using an online sidereal calculator like this.

Another important discrepancy between tropical and sidereal astrology is planetary rulership and influence. Unlike tropical astrology, sidereal astrology does not acknowledge the influence of Uranus, Neptune or Pluto on the individual or the individual’s birth chart. These outer planets are not visible to the naked eye and their distance from earth lessens their effect of life on it.


About editor 3017 Articles
Writer and Journalist living in Canada since 1987. Tamil activist.

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