top of page

All blog posts and images on this website are

protected by copyright, and all rights are reserved.

You may not copy, republish or distribute

without permission.


Zodiac Confusions: Astronomy, Sidereal, and Tropical

Pictured above is a symbolic image representing a constellation that astronomers have named Orphiuchus, which has stirred up both controversy and confusion for skeptics and believers in astrology. So first, let me say that even though it was ASTROLOGERS who invented the science of astronomy in ancient times, the two disciplines today are not always mirrors of each other. Let's try to explain.

Back when humans believed that the Sun rotated around the Earth, astrologers noticed a band, or swath, of stars through which the Sun appeared to move. In reality it was our viewpoint from Earth that was moving, and seeing different configurations of stars as the backdrop for the Sun. These configurations became known as constellations, and the band of stars in its entirety was called the zodiac -- which means the "way of life."

Even in today's world with sophisticated telescopes and other measuring devices, the astronomical constellations do not have very precise boundaries. And while perhaps the term stellar drift is mostly used in science fiction contexts, as astronomers' visual and measurement observations get ever more refined it is reasonable to propose that the imprecise astronomical constellations are shifting enough to form additional configurations along that zodiacal band.

Orphiuchus is one of the relatively "new" constellations, having been defined and named in 2011. Astrologers, however, are not rushing to adjust Sun signs and make room for Orphiuchus on astrology charts.

The Sidereal and Tropical Zodiacs

The sidereal zodiac -- pronounced sih-DEER-ree-uhl -- is used in the Vedic (also called Jyotish) astrology system that originated in India. This system uses the fixed stars to orient their zodiac, and in some of the more complex readings, fixed stars such as Spica, Sirius, Canopus, Alpha Centauri, Regulus, and others may be used to provide refined interpretations.

The tropical zodiac is the more popular system of astrology used in the western world. Now drawing heavily on Greco-Roman mythology for names of planets, asteroids, and constellations, the tropical zodiac feels more familiar to clients and Western astrologers alike. The tropical system was originally based on Earth's seasons for reference, with 0 degrees of Aries marking both the beginning of the zodiac and the beginning of Spring.

The sidereal and tropical zodiacs are said to have once been in perfect alignment way back around 285 CE. But they have been diverging ever since, and at this point are about 23-24 degrees different. Given that astrologers hold to the idea that each zodiac sign is only 30 degrees "wide" to start with, you can see how this would make for incompatibility between these two zodiacs.

Knowing that the tropical and sidereal zodiacs are so different can be helpful when a client says their reading doesn't fit them at all. Of course, the problem is more likely that the birth time is wildly inaccurate. But once in a while the problem is that the other zodiac system would serve them better.

The first astrologer I ever consulted practiced Vedic astrology and told me I was a Sagittarius. I was shocked. How could that be?

It was this crazy difference in degrees, or math, that pushed me back from my birth Sun being at 15 degrees Capricorn to being at about 23 degrees of Sag. It was extremely disorienting because I have never really fit much of the description for a Sag (college teaching and publishing not withstanding -- but those experiences are easily explained by having Sag rule my 2nd house of personal income).

So the moral of this story is that it is important to know which zodiac is being referred to when reading anything that purports to be about astrology. And by the way, on this blog, my reference point is always the western (tropical) zodiac unless otherwise stated.


By Tags
No tags yet.
bottom of page