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copyright ©1998-2008 by Richard Nolle
last revised APR 16, 2008

Every now and then, some astronomer creates a flap by claiming that astrology is all wrong because the signs don't line up with the constellations. And if I had a dime for every time some New Ager claimed that "this is the dawning of the Age of Aquarius" . . . well, I could probably buy the rights to the Broadway musical that set those words to music back in the 1960s. In this instance, the astronomer types and the New Age types are both wrong. Despite the fact that their arguments are based on an irrefutable natural phenomenon (the 'precession of the equinoxes'), they have it all so turned around that they don't know what they're talking about. And therein lies a tale . . .

It is true that the zodiacal signs and constellations are not in the same place in our time - or in any other epoch, due to the unequal length of each constellation versus the equal length of each sign. Exactly how far apart they are depends on which definition of constellations you use, and there are plenty of those to choose from. Fortunately there's only one definition of signs to consider, because astrologers have been very consistent on that point for a couple thousand years now. But to illustrate - see below - let's use the constellations as recognized by modern astronomy. These were defined in their present form by the International Astronomical Union (IAU) in 1930. A plot of the heavens for the beginning of the 21st Century - that's January 1, 2001 at midnight Universal Time - shows the Sun in the IAU constellation Sagittarius. (The Sun is the yellow circle with a dot in the middle, located in the center of the picture; which incidentally was produced using Maris Multimedia's RedShift 2 astronomy software.)1 Yet a glance at an astrological ephemeris for the same date - or a look at those silly sun sign columns in the comics section of your daily newspaper - shows the Sun to be in the sign Capricorn on that date. How can this be?

JAN 1, 2001 starmap

The answer, quite simply, is that there are two distinct zodiacs. One is a zodiac of signs, the other a zodiac of constellations. Each is divided into twelve sectors named (in order) as follows: Aries, Taurus, Gemini, Cancer, Leo, Virgo, Libra, Scorpio, Sagittarius, Capricorn, Aquarius and Pisces. Other than their names, these two zodiacs have nothing at all in common. The zodiac of signs - known as the tropical zodiac - has twelve equal sectors, each thirty degrees in length. The twelve sectors of the zodiac of constellations - known as the sidereal zodiac - are in most cases of unequal length. The exact length and starting point of each of these twelve constellations depends on whose definition is used. And there are many to choose from, because unlike the tropical zodiac (of which there has been only one since its inception a couple thousand years ago), there are quite a few different sidereal zodiacs. For example, with the 'Johnny-come-lately' IAU sidereal zodiac, the length of each constellation varies from a minimum of 18 degrees (Libra) to a maximum of 46 degrees (Virgo). Here's the tale of the tape: Aries (24o), Taurus (36o), Gemini (28o), Cancer (21o), Leo (35o), Virgo (46o), Libra (18o), Scorpio (31o), Sagittarius (30o), Capricorn (28o), Aquarius (25o), and Pisces (38o).2 By the simple fact that the 30o-wide sign Aries can't fit into the 24o-wide constellation of the same name, you can see that it's plainly impossible for the signs and constellations to be in exactly the same place!

It is possible for the starting points of a given sign and constellation to line up, even though the rest of the sidereal and tropical zodiac won't match up due to the unequal boundaries of the various constellations. Over 2000 years ago, in an epoch when sidereal Aries and tropical Aries were roughly in the same segment of the heavens, astrologers in the Western world recognized that the signs were slipping backward with respect to the constellations at a rate of about one degree every 72 years. In other words, if the beginning of the sign Aries (the zero degree point) was perfectly aligned with the beginning of the constellation Aries on a given date, then some 72 years later the 0 degree point of the sign Aries would fall in the last degree of the preceding constellation (Pisces). Recognizing this slippage, astrologers also recognized that their system was tied to the signs - not to the constellations. So they promptly ignored the constellations way back then.

Astronomers and others from Voltaire on who have assailed astrology over the discrepancy between signs and constellations have committed a fundamental error. They have criticized something without bothering to investigate it. Anyone who took the time to study astrology would certainly be aware that modern astrological tradition in the Western world descends directly from the Greek astrologer Claudius Ptolemy. In his Tetrabiblos, written in the 2nd Century CE - that's 2nd Century AD, for you non-ecumenical types - Ptolemy clearly laid the signs versus constellations question to rest. "The beginning of the whole zodiacal circle," he affirms, "is therefore assumed to be the sign of Aries, which commences at the vernal equinox."3 Just to make sure even the astronomers wouldn't miss it, Ptolemy repeats the point: "The beginnings of the signs," he writes, "are to be taken from the equinoctial and tropical points."4 Ptolemy didn't make this up out of the blue, all by his lonesome: "This rule," he notes, is "clearly stated by writers on the subject."5 Ptolemy had access to the Great Library at Alexandria (where he lived), and therefore can be assumed to have had a nodding acquaintance with the astrological literature of his day. And far from being an original writer, all he did was summarize and organize the astrology of that era - an astrology that was by then already centuries old. From this it is evident that astrologers before and during Ptolemy's time were working with a zodiac of signs - not a zodiac of constellations. (As early as the 5th Century BCE, some Greek and Babylonian astrologers were working with a zodiac divided into twelve equal segments based on the equinoxes and solstices: a zodiac of signs, not constellations, in other words.)

So there you have it, straight from the historical figure who is universally acknowledged as the Father of modern Western astrology: it's the signs, as defined by the equinoctial and tropical points (and specifically the vernal equinox), that count - not the constellations. You might think that anyone who'd criticize astrology on account of the discrepancy between signs and constellations would bother to get acquainted with some basic history before going on the warpath. But then you'd be making the mistake of assuming that a propagandist has any interest in the truth in the first place. And that's just what anyone who attempts to debunk astrology on the grounds of the signs-versus-constellations argument is: a propagandist, one who aims to sway the minds and hearts of people without regard for the facts. In a word, that whole red herring has no basis other than ignorance. (I'm ruling out malevolence because the astronomers I've met seem to be pretty decent folks.)

There's a delicious irony in astronomers criticizing astrologers for ignoring the constellations. It's that the astronomers base their entire system of celestial coordinates on the very same point Ptolemy declared as the beginning of the zodiac of signs - the northern vernal equinox, the point in the heavens (as seen from Earth) where the Sun appears to be at the beginning of spring in the northern hemisphere. Let me see, how does that work? If we astrologers use the vernal equinox as a starting point, it's wrong - but if you astronomers use it, it's right?? If that's the case it's a cause for celebration, because it proves that at least some of us can have our cake and eat it too! Although it appears you have to be an astronomer to pull it off . . .

The celestial sphere: vernal equinox, 2001The best way to illustrate this is with a picture, of course. What we have here - courtesy of RedShift 2 again - is an image of the celestial sphere viewed from the outside, so you can see as much of the whole thing as possible all at once. (In this case, the illustration shows the Sun's position at the moment of the vernal equinox in the year 2001.) The celestial sphere is an imaginary construct, which represents the way the Sun, Moon, planets, stars etc. appear to us here on Earth. Envision a great crystal sphere with the Earth at its center and everything else out in space lying on (or projected through) the surface of that sphere, and you've pretty well got the picture. The celestial sphere of astronomy projects Earth's poles and equator out into space to lay out its prime coordinates. Distance north or south of the celestial equator is measured in what's called declination (degrees, minutes and seconds), while distance along the equator is measured in what's called right ascension (degrees, minutes and seconds, subdivided into hours). This system is the spherical grid shown in the image, resembling the circles of latitude and longitude you'd see on a globe of the Earth. The red circle cocked at an angle to the celestial equator in the figure is known as the ecliptic. It's the plane of Earth's orbit around the Sun. As seen from Earth, it's the apparent path the Sun takes through the heavens. The ecliptic circle is inclined to the equator because Earth's poles are tilted in relation to the path our home planet follows in its orbit around the Sun. In the illustration, the point where the ecliptic circle and the celestial equator meet is the apparent location of the Sun at the moment of the northern vernal equinox - the beginning of spring in the northern hemisphere, in other words. No matter what constellation this point may fall in, it marks the beginning of the great reference circles of astronomy and astrology. On the celestial equator, this is the zero point of right ascension. Measured along the ecliptic circle, this same point is the beginning (0 degrees) of the sign Aries. (The ecliptic circle is divided into degrees, minutes and seconds of ecliptic longitude; distance north or south of this plane is measured in degrees, minutes and seconds of ecliptic latitude.) So you see, one and the same point marks the beginning of both the astronomical coordinate system and the astrological zodiac of signs.

A horoscope for the 2001 vernal equinoxAs far as the signs versus constellations controversy goes, the long and the short of it is that the signs as defined by modern astrology are correct as they are - regardless of where they may appear to be with respect to the constellations. Which means that those sun sign columns in the newspapers and magazines do have the correct starting and ending dates. From that point on they're all wrong of course, simply because sun signs are a nonsensical parody of real astrology. (Sun sign astrology: there's an oxymoron for you.) Real astrology uses a map of the heavens calculated for the exact time, date and place of a person's birth. It's called a natal horoscope, and it plots the position of the Sun, Moon and planets - not just the sign occupied by the Sun. For example, here's a natal horoscope plotted by Matrix's WinStar Plus6 for the moment of the 2001 vernal equinox (UT 1:31 PM March 20, 2001) at the location of the Great Pyramid. In it, you'll see not only the by now familiar symbol representing the Sun (the circle with a dot in the middle), but the symbols representing the Moon and planets, the signs, etc. (If you're not conversant with these, see Astroglyphs: An Astrological Symbols Guide.) Whereas such a horoscope is virtually as individual as your fingerprints, the silly sun sign 'horoscopes' are a twelve-sizes-fit-all proposition. You share your sun sign with about a half-billion other people on planet Earth at the moment. How individual is that? The very notion that sun signs could offer any meaningful personal information is ridiculous on the face of it!

Having laid to rest the tired old signs versus constellations argument, what about all this Age of Aquarius stuff? Well, that brings us to Precession, the Movie . . .

NOTE: My April 16, 2008 update fixes broken links caused mostly by pages or sites moving over the years. Also, some HTML coding errors have been eliminated.



1Maris Multimedia, San Rafael CA, 1995. (See their website for more information.)
2Dean, Geoffrey et al., Recent Advances In Natal Astrology. Subiaco, Australia: Analogic, 1977, p. 49.
3Ashmand, J. M. trans., Ptolemy's Tetrabiblos. North Hollywood CA: Symbols & Signs, 1976, p. 21.
4ibid., p. 37.
6Matrix Software, Big Rapids MI, 1997. (See their website for more information.)


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