Sidereal Calculations


and the


First Point of Aries

(from the Swiss Ephemeris webpage)


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Thanks to Juan Ant. Revilla, San Jose, Costa Rica, who gave us this precious bibliographic hint.


The problem of defining the zodiac

One of the main differences between the western and the eastern tradition of astrology is the definition of the zodiac. Western astrology uses the so-called tropical zodiac which defines 0° Aries as the vernal point (the celestial point where the sun stands at the beginning of spring). The tropical zodiac has actually nothing to do with the star constellations of the same names. Based on these star constellations is the so-called sidereal zodiac, which is used in eastern astrology. Because the vernal point slowly moves through these constellations and completes its cycle once in 26000 years [24,000 years according to Swami Yukteswar, ed.], tropical Aries moves through all sidereal signs, staying in each one for roughly 2160 years. Currently, the vernal point, and the beginning of tropical Aries, is located in sidereal Pisces. In a few hundred years, it will enter Aquarius, which is the reason why the more impatient ones among us are already preparing for the age of Aquarius.

While the definition of the tropical zodiac is clear and never questioned, sidereal astrology has quite some problems in defining its zodiac. There are many different definitions of the sidereal zodiac, and they differ by several degrees. At a first glance, all of them look arbitrary, and there is no striking evidence – from a mere astronomical point of view – for anyone of them. However, a historical study shows at least, that all of them  stem from only one sidereal zodiac. On the other hand, this does not mean that it is simple to give a precise definition of it.

Sidereal planetary positions are usually computed from an equation similar to:

sidereal position = tropical position – ayanamsha,

where ayanamsha is the difference between the two zodiacs and changes with time. (Sanskrit ayanâmsha means ”part of a path”; the Hindi form of the word is ayanamsa with an s instead of sh.) ”

The ayanamsha is computed from the ayanamsha at a starting date (e.g. 1 Jan 1900) and the speed of the vernal point, the so-called precession rate.

The zero point of the sidereal zodiac is therefore traditionally defined by the equation:

sidereal Aries = tropical Aries – ayanamsha

and by a date for which this equation is true.

The Swiss Ephemeris allows for about twenty different ayanamshas, but the user can also define his or her own ayanamsha.


The Babylonian tradition and the Fagan/Bradley ayanamsha

There have been several attempts to calculate the zero point of the Babylonian ecliptic from cuneiform lunar and planetary tablets. Positions were given from some sidereally fixed reference point. The main problem in fixing the zero point is the inaccuracy of ancient observations. Around 1900 F.X. Kugler found that the Babylonian star positions fell into three groups:

ayanamsha = -3°22´, t0 = -100

ayanamsha = -4°46´, t0 = -100 Spica at 29 vi 26

ayanamsha = -5°37´, t0 = -100

In 1958, Peter Huber reviewed the topic in the light of new material and found:

ayanamsha = -4°34´ +/- 20´, t0 = –100 Spica at 29 vi 14

The standard deviation was 1°08’

In 1977 Raymond Mercier noted that the zero point might have been defined as the ecliptic point that culminated simultaneously with the star Eta Piscium (Al Pherg). For this possibility, we compute:

ayanamsha = -5°04’46”, t0 = –129 Spica at 29 vi 21

Around 1950, Cyril Fagan, the founder of the modern western sidereal astrology, reintroduced the old Babylonian zodiac into astrology, placing the fixed star Spica near 29°00 Virgo. As a result of ”rigorous statistical investigation” (astrological!) of solar and lunar ingress charts, Donald Bradley decided that the sidereal longitude of the vernal point must be computed from Spica at 29° vi 06'05" disregarding its proper motion. Fagan and Bradley defined their ”synetic vernal point” as:

ayanamsha = 24°02’31.36” for 1 Jan. 1950 with Spica at 29 vi 06'05" (without aberration)

(For the year –100, this ayanamsha places Spica at 29 vi 07’32”.)

Fagan and Bradley said that the difference between P. Huber’s zodiac and theirs was only 1’. But actually (if Mercier’s value for the Huber ayanamsha is correct) it was 7’.

According to a text by Fagan (found on the internet), Bradley ”once opined in print prior to "New Tool" that it made more sense to consider Aldebaran and Antares, at 15 degrees of their respective signs, as prime fiducials than it did to use Spica at 29° Virgo”. Such statements raise the question if the sidereal zodiac ought to be tied up to one of those stars. Today, we know that the fixed stars have a proper motion, wherefore such definitions are not a good idea, if an absolute coordinate system independent on moving bodies is intended. But the Babylonians considered them to be fixed.

For this possibility, Swiss Ephemeris gives an Aldebaran ayanamsha:

ayanamsha with Aldebaran at 15ta00’00” and Antares at 15sc00’17” around the year –100.

The difference between this ayanamsha and the Fagan/Bradley one is 1’06”.

The Hipparchan tradition

Raymond Mercier has shown that all of the ancient Greek and the medieval Arabic astronomical works located the zero point of the ecliptic somewhere between 10 and 22 arc minutes east of the star Zeta Piscium. This definition goes back to the great Greek astronomer Hipparchus. How did he choose that point? Hipparchus said that the beginning of Aries rises when Spica sets. This statement was meant for a geographical latitude of 36°, the latitude of the island of Rhodos, which Hipparchus’ descriptions of rises and settings are referred to.

However, there seems to be more behind it. Mercier points out that according to Hipparchus’ star catalogue the stars alpha Arietis, beta Arietis, zeta Piscium, and Spica are located in precise alignment on a great circle which goes through that zero point near zeta Piscium. Moreover, this great circle was identical with the horizon once a day at Hipparchus’ geographical latitude of 36°. In other words, the zero point rose at the same time when the three mentioned stars in Aries and Pisces rose and at the same time when Spica set.

This would of course be a nice definition for the zero point, but unfortunately the stars were not really in such precise alignment. They were only assumed to be so.

Mercier gives the following ayanamshas for Hipparchus and Ptolemy (who used the same star catalogue as Hipparchus):

ayanamsha = -9°20’ 27" 27 June –128 (jd 1674484) zeta Piscium 29pi33’49” Hipparchos

(According to Mercier’s calculations, the Hipparchan zero point should have been between 12 and 22 arc min east of zeta Piscium, but the Hipparchan ayanamsha, as given by Mercier, has actually the zero point 26’ east of zeta Piscium. This comes from the fact that Mercier refers to the Hipparchan position of zeta Piscium, which was at least rounded to 10’ – if otherwise correct.)

If we used the explicit statement of Hipparchus that Aries rose when Spica set at a geographical latitude of 36 degrees, the precise ayanamsha would be -8°58’13” for 27 June –128 (jd 1674484) and zePsc would be found at 29pi12’, which is too far from the place where it ought to be.

Mercier also discusses the old Indian precession models and zodiac point definitions. He notes that, in the Sűrya Siddânta, the star zeta Piscium (in Sanskrit Revatî) has almost the same position as in the Greek sidereal zodiac, i.e. 29°50’ in Pisces. On the other hand, however, Spica (in Sanskrit Citra) is given the longitude 30° Virgo. This is a contradiction, either Spica or Revatî must be considered wrong.

Moreover, if the precession model of the Sűrya Siddânta is used to compute an ayanamsha for the date of Hipparchus, it will turn out to be –9°14’01”, which is very close to the Hipparchan value. The same calculation can be done with the Ârya Siddânta, and the ayanamsha for Hipparchos’ date will be –9°14’55”. For the Siddânta Shiromani the zero point turns out to be Revatî itself. By the way, this is also the zero point chosen by Copernicus! So, there is an astonishing agreement between Indian and Western traditions!

The same zero point near the star Revatî is also used by the so-called Ushâshashî ayanamsha which is still in use. It differs from the Hipparchan one by only 11 arc minutes.

ayanamsha = 18°39’39.46 1 Jan. 1900 Ushâshashî

zePsc (Revatî) 29pi50’ (today), 29pi45’ (Hipparchus’ epoch)

The Greek-Arabic-Hindu ayanamsha was zero around 560 AD. The tropical and the sidereal zero points were at exactly the same place. Did astronomers or astrologers react on that event? They did! Under the Sassanian ruler Khusrau Anűshirwân, in the year 556, the astronomers of Persia met to correct their astronomical tables, the so-called Zîj al-Shâh. These tables are no longer extant, but they were the basis of later Arabic tables, the ones of al-Khwârizmî and the Toledan tables.

One of the most important cycles in Persian astronomy/astrology was the one of Jupiter, which started and ended with the conjunctions of Jupiter with the sun. This cycle happened to end in the year 564, and the conjunction of Jupiter with the Sun took place only one day after the spring equinox. And the spring equinox took place precisely 10 arcmin east of zePsc. This may be a mere coincidence from a present-day astronomical point of view, but for scientists of those days this was obviously the moment to redefine all astronomical data.

Mercier also shows that in the precession model used in that epoch and in other models used later by Arabic Astronomers, precession was considered to be a phenomenon connected with ”the movement of Jupiter, the calendar marker of the night sky, in its relation to the Sun, the time keeper of the daily sky”. Such theories were of course wrong, from the point of view of today’s knowledge, but they show how important that date was considered to be.

After the Sassanian reform of astronomical tables, we have a new definition of the Greek-Arabic-Hindu sidereal zodiac, and a very precise one (this is not explicitly stated by Mercier, however):

ayanamsha = 0 18 Mar 564, 7:53:23 UT (jd /ET 1927135.8747793) Sassanian

zePsc 29pi49'59"

The same zero point then reappears with a precision of 1’ in the Toledan tables, the Khwârizmian tables, the Sűrya Siddhânta, and the Ushâshashî ayanamsha.

(Besides the synchronicity of the Sun-Jupiter conjunction and the coincidence of the two zodiacs, it is funny to note that the cosmos helped the inaccuracy of ancient astronomy by ”rounding” the position of the star zePsc to precisely 10 arc minutes east of the zero point! All Ptolemean star positions were rounded to 10 arc minutes.)

The Spica/Citra tradition and the Lahiri ayanamsha


After the Babylonian and the Greek definitions of the zero point, there is a third one which fixes the star Spica (in Sanskrit Citra) at 0 Libra. This definition is today the most common one in Hindu astrology. It is named after N.C. Lahiri:

ayanamsha = 22°27’37.7 1 Jan. 1900 Lahiri, Spica at 0 Libra

However, and this is very confusing, the same definition seems to have used in Babylon and Greece as well. While the information given in the chapters about the Babylonian and the Hipparchan traditions are based on analyses of old star catalogues and planetary theories, the consideration of 22 ancient Greek and 5 Babylonian birth charts leads to different conclusions: they fit better with Spica at 0 Libra, than with Aldebaran at 15 Taurus and Spica at 29 Virgo (Fagan/Bradley)! See Nick Kollerstrom, in Culture and Cosmos in 1997 (Vol. 1, n.2).

Were there a different zodiacs for astronomical and astrological purposes? May be, Spica was chosen as an anchor star for reasons of more convenience, but it was not originally meant to be located precisely at 0 Libra.

The definition by Spica at 0 Libra would be so simple, clear, and convincing that, had it really been intended, it would probably never have been given up and the other definitions would never have been taken into consideration.

1 January 1920 22°45´
1 January 1930 22°53´
1 January 1940 23°01´
1 January 1950 23°10´
1 January 1960 23°18´
1 January 1970 23°26´
1 January 1980 23°35´
1 January 1990 23°43´
1 January 2000 23°51´


Yukteswar ayanamsha

excerpted from the
Crystal Pages Jyotish Primer

A brief account of the Yukteshwar ayanamsha is provided here. In the year 1894, Swami Yukteshwar Giri (guru of Parmahansa Yogananda who authored the famous "Autobiography of a Yogi" and started the Self-Realization Fellowship in California) wrote a small book named "The Holy Science". It holds gems of much spiritual value, but it also has a very interesting and 'different' perspective on the 'Chaturyuga' cycles.

In this very book, he also talks about how the Yugas are linked with the cycle of precession.... The jyotishis use the constellational zodiac or visible zodiac to demarcate the rashis or bhachakra. When a planet is seen in the constellational region of Scorpio, up in the sky, the jyotishi considers the planet to be in Scorpio. In contrast, the tropical zodiac used by western astrology is geared to the cycle of seasons and the first point of Aries in this system is considered to be the moment of equinox or equal night and day in spring (in the northern hemisphere, or the autumn in southern hemisphere); this is based on the declinational (ayana) journey of the apparent sun (actually, the earth). The two zodiacs slide away from each other at the rate of about 1 degree in 72 years. This motion is called ayanamsha and there are many values recommended by different scholars for this 'correction' that is applied to tropical longitudes to derive sidereal values.

Why is it necessary to work from the tropical longitudes? This is because, the moment of equinox is a definite epoch which is objectively and easily measurable; however, the first point of sidereal Aries is not so easily discernible and hence there remains some room for variations of opinions. This is why we have a choice of so many popular ayanamshas: Lahiri, Fagan, Raman, Krishnamurthi, Devdutta and many more.

Swami Giri, in his 1894 work, referred to contemporary astronomical books (presumably ephemeris or panchangs without specifying which) and gave the value of:


ayanamsha = 20 deg 54 min 36 sec for the spring equinox of 1894


and identified


AD 499 as the year of coincidence of the two zodiacs. (ayanamsha = 0)


He obviously used a value of:


54 sec per year for the annual motion of ayanamsha precession.


[This would correspond to a 24000 year precession cycle average rate: 24000 ÷ 360°=66.667 years for 1° which equals 54 seconds/year. Apparently Yukteswar was using the  Sűrya Siddânta as his source because according to the Sűrya Siddânta modern commentary*, the initial point of the sidereal sphere coincided with the mean vernal equinox after 3600 years of the Kali Yuga  had expired (~499 A.D.) and the annual precession is given as 54". Current accepted Hindu chronology has the Kali Yuga beginning at 3101BC or 3102BC depending on the source. Therefore 3101BC + 3600 years equals 499AD. It is interesting to note that when using "the explicit statement of Hipparchus (see above) that Aries rose when Spica set at a geographical latitude of 36 degrees, the precise ayanamsha would be -8°58’13” for 27 June –128" and you would arrive at a date of around 517AD (using the slightly slower rate of 50"/year that would have been correct for that era) which is less than 20 years from Yukteswar's date for a zero ayanamsha of 499AD. If the precession model of the Sűrya Siddânta is used to compute an ayanamsha for the date of Hipparchus, it will turn out to be –9°14’01”, which is very close to the Hipparchan value. Using this model (54"/year) you would arrive at 487AD for a zero ayanamsha. Even closer still would be Mercier's value for the Hipparchus/Ptolemy ayanamsha of -9° 20' 27" which would give a zero date of ~495AD., ed. note].


* SuryaSiddhanta, Ebenezer Burgess translator, Journal of the American Oriental Society, Volume 6, New Haven, 1860


Modern scientific observation attributes a value of approximately 50.25 to 50.3 seconds for this quantity (the annual motion of precession of equinoxes is not a constant term and varies over time in a gradually cyclical manner).

Now, if we divide 20d 54m 36s (=75276 sec; the value of ayanamsha for 1894) by 50.28, we get a value very close to the year 397 which is the year of coincidence recommended by Dr. B.V. Raman in late 1930s. In 1999, Raman's ayanamsha gives positions of planets that are about 6 minutes ahead of Yukteshwar's because of the 3-4 seconds annual differences in the values of annual motion adopted since 1894.  This is a minor difference and the similarity in values for these two ayanamshas recommended by these two stalwarts separated by almost fifty to sixty years is simply remarkable. I am not aware of nor have I read anywhere if Prof. Raman's ayanamsha was inspired by the value given by Shri Yukteshwar Giri or if it was independently derived by the Late eminent Prof. Raman.

For those individuals who use the Yukteshwar ayanamsha option in their jyotish software, it would be advisable to check if the value of
ayanamsha turns out to be 20d 54m 36s for vernal equinox of 1894 (March 21/22)*. Fine tuning of the software value, if permitted, to bring it to that quoted by Swami Giri would be helpful.

JYOTISH PRIMER by Rohin Iranjan /Crystal Pages -- © All rights reserved, since 1980


* The Indian Astronomical Ephemeris For The Year 1981 (Delhi, 1980) gives the position of zeta Piscium on 1.432 January 1981 as 19° 36' 40.64" ecliptic longitude which is a difference of 1° 17' 56" from the 1894 value. This would correspond to 4676 seconds of precession over an 87 year period which equals a rate of ~53.75"/year, ed. note.



The Galactic Center                               

As said before, there is a very precise definition for the tropical ecliptic. It starts at one of the two intersection points of the ecliptic and the celestial equator. Similarly, we have a very precise definition for the house circle which is said to be an analogy of the zodiac. It starts at one of the two intersection points of the ecliptic and the local horizon. Unfortunately there is no such definition for the sidereal zodiac. Or can a fixed star like Spica be important enough to play the role of an anchor star?

One could try to make the sidereal zero point agree with the Galactic Center. The Swiss astrologer Bruno Huber has pointed out that the Galactic Center enters a new tropical sign always around the same time when the vernal point enters the next sidereal sign. Around the time, when the vernal point will go into Aquarius, the Galactic Center will change from Sagittarius to Capricorn. Huber also notes that the ruler of the tropical sign of the Galactic Center is always the same as the ruler of the sidereal sign of the vernal point (at the moment Jupiter, will be Saturn in a few hundred years).

A correction of the Fagan
ayanamsha by about 2 degrees or a correction of the Lahiri ayanamsha by 3 degrees would place the Galactic Center at 0 Sagittarius. Astrologically, this would obviously make some sense. Therefore, we add an ayanamsha fixed at the Galactic Center:

Galactic Center at 0 Sagittarius

The other possibility – in analogy with the tropical ecliptic and the house circle – would be to start the sidereal ecliptic at the intersection point of the ecliptic and the galactic plane. At present, this point is located near 0 Capricorn. However, defining this point as sidereal 0 Aries would mean to break completely with the tradition, because it is far away from the traditional sidereal zero points.


Nick Anthony Fiorenza has introduced another version of the Galactic Ayanamsa on his website. It is based on the harmonic math and spherical geometry of the astrophysical spheres involved (specifically our solar system’s current location and orientation (tilt) in our galaxy / the galactic equatorial axis / Gate of God), rather than on star locations as seen from Earth.


Just as Earth is tilted as it orbits the sun, so too is our solar system tilted as it orbits around the center of our galaxy. This means that the ecliptic plane is tilted (about 60°) within our galaxy's equatorial plane. This creates another intersecting line, one which remains stationary (relative to Earth's precessional period). This axis is called the galactic equatorial axis and it is the fixed axis of the Holy Cross. The primary reference point of this axis is the galactic equatorial node (GEN), which resides at 5° sidereal Sagittarius. This node is called the "Gate of God." Its opposite point, the anti-GEN, resides at 5° sidereal Gemini and it is called the "Gate of Man."


The changing relationship between these two axes (the moving vernal axis and the fixed galactic axis) creates the "Cycle of the Holy Cross." As the vernal point moves around the ecliptic, it changes its angular relationship to the fixed GEN. The vernal point currently resides at the 3/4 point (270°) in its cycle, making the vernal axis exactly perpendicular to the galactic axis, thus creating a perfect cross in the ecliptic--the Erect Holy Cross.


Copyright © 2001-2004 Nick Anthony Fiorenza, All Rights Reserved



Thus, the Galactic Ayanamsa is defined by setting the GEN (Gate of God) to exactly 5° 00’ 00” sidereal Sagittarius. The Galactic Ayanamsa is 25° 00’ 00” @ 2000 A.D. Thus, 0° Tropical Aries currently resides at 5° 00’ sidereal Pisces @ 2000 A.D. and the tropical zodiac has drifted from the fixed sidereal zodiac by 25° 00’ 00” based upon the Galactic Ayanamsa.

To further compound the problem of zodiacal reckoning, we must recognize that the rate of Earth's precession is not a constant. It is accurate to say the last erect Holy Cross had occurred exactly 180° degrees ago in the precessional cycle, but we can only estimate that to have been 11,000 to 13,000 years ago. The rate of precession may vary significantly over long periods of time, or even oscillate around some harmonic ideal. There are many continuously changing astronomical factors that affect the rate of precession.

"The Great World Cycle," or "Earth's Great Year," as Earth's precessional cycle is sometimes called, is estimated to be between 23,000 and 26,000 solar years--often rounded to the latter figure. The 25,920 figure, often seen, is a natural harmonic ideal found in quantum math. Another quantum number of significance is 22,680, quite close to the 23,000 figure. These are all academic figures however: Earth's current rate of precession is calculated to be 25,867 years. This is about 1° every ~71.85 years, or 0° 00' 50.26" per year.

Cayce Readings


The Tropical zodiac has a precise starting point at the northern hemisphere spring and southern hemisphere fall equinox. But what about the sidereal zodiac? A zodiac requires a fiducial point on the circle from which measurements are made. Various measurements from specific stars were used in Mesopotamia to designate the initial points of zodiac signs. However, these stars were not exactly 30 degrees and zero minutes from each other, which leaves us with a zodiac with hazy sign boundaries.


Of the bright stars that lie close to the ecliptic, Spica is virtually the only candidate for a fiducial star that is located near a sign junction, and this junction happens to be just at the center of the sidereal zodiac between Virgo and Libra. Perhaps of greater interest is that Spica is only minutes in longitude from bright Arcturus to the north. Edgar Cayce gave great importance to Arcturus as evidenced from these quotes from his readings:



Arcturus magnifies the force of will. 5749-14 Arcturus is that which may be called the center of this universe.  For Arcturus is that junction between the spheres of activity as related to cosmic force, and is that about which this particular environ or sphere of activity rotates, or is a relative source of activity.


440-3 (Produce etheronic energy) from a combination of crystals - the ray that came from setting of the prismatic influences from high heating - from the Sun, or better from Arcturus.

“For Arcturus is the way, the door out of this system.” (2454-3)


“Not that the Sun as the center of the solar system is all there is. For the entity has attained to that realm even of Arcturus, or that center from which there may be the entrance into other realms of consciousness.” (2823-1)


“Arcturus is that which may be called the center of the universe, through which individuals pass and at which period there comes a choice of the individual as to whether it is to return [to earth] or to pass on to [other systems]." (5749-14)


“Arcturus is that junction between spheres of activity as related to cosmic force, and is that about which this particular sphere of activity rotates...” (263-15)


"This building on the pyramid lasted for a period of one hundred years, as now termed. It was formed according to that which had been worked out by Ra Ta in the mount, as related to the position of the stars about which this particular solar system circles in its activity....going toward what? That same name to which the priest was banished, Libya-or the constellation of Libra." (294-151)


So, at least according to Edgar Cayce, the degree of Arcturus (and Spica) is of critical importance for the evolution of mankind. Does the longitudinal degree of Spica–Arcturus—the junction point between Virgo and Libra— mark a critical wave emanation point for the Sidereal zodiac? Just opposite this point is zero degrees of Aries.



Finding the Point of Wave Emanations


Since it is the peaks and troughs of waves that may define signs, how do we know exactly where high and low points occur in the zodiacal circle? The exact phasing of zodiacal waves, if they exist, cannot be easily observed. The key areas in question are the current areas of overlap between the Tropical and Sidereal zodiacs. (See figure 2 below) These areas are approximately five to seven degrees in length depending on the ayanamsa (the difference between the Tropical and Sidereal zodiacs) and the modern year in question.



 Your ALT-Text here



If the final degrees of a Tropical sign behave more like the following Tropical sign in relation to polarity, the modes and elements, then this is evidence for a sidereal zodiac of wave influences. If the early degrees of Sidereal signs resemble the preceding sign, then this points to harmonic waves linked to the equinox points.


Because the area of overlap between the zodiacs at present is only 1/5 of a sign, and harmonic effects would diminish toward the ends of signs, it is very difficult to judge which zodiac might be the most accurate when only personal opinion and observation are used for measurement. It may be that the characteristics of polarity, the modes and trigons cannot be observed at all for the first five degrees and final five or six degrees of a sign. This is precisely the current overlap of the Tropical and Sidereal zodiacs.



In summary a sign of the zodiac may be made up of:


(1) Harmonics which correlate with polarity, trigons and qualities. (Note: Other harmonics may exist such as the 27 Indian nakshatras or the 28 medieval lunar mansions.)


(2) Influences which relate directly to the domicile lords and exalted planets in signs via a cosmic connection whose operation we don't understand at present.


(2) Individual stars which may affect variable degrees depending on how bright the star is. A bright star such as Spica may influence a two degree area whereas the effect of a small dim star may be limited to less than a degree.


(3) The possible overall effect of the actual constellations. This would cause a blending across signs. For example Virgo extends into two thirds of sidereal Libra. The actual constellation of the scales falls in the last ten degrees of Libra. Are the first two thirds of Libra different than the last third? (Or is there a noticeable difference between early and later Tropical Scorpio—the current constellational boundary of Virgo and Libra?)


If effects come from the actual stars and/or constellations, then the meanings of Tropical signs will shift over the centuries, whereas sidereal signs will remain stable. Another possibility is that harmonics correlate with signs measured from the equinox, but the effects of planetary domiciles belong to the sidereal zodiac. This would mean that over the centuries the effects of polarity, trigons and qualities would phase in and out of the sidereal signs while the sign effects which correlate with the planets would remain stable.


The easiest solution would be if harmonics were tied to a particular fiducial star such as Spica; then the effects of the stars and constellations would remain stable over the centuries in a sidereal zodiac. In the Tropical zodiac the stars and constellations will always shift over time in relation to the signs. It is still an unknown how the domicile lords operate in the zodiac, though I've found the correlation much easier to make in the sidereal zodiac. A few Tropical astrologers have actually told me that they don't believe there is any correlation at all between planets and zodiac signs!


At this time we are still faced with centuries of unanswered questions about the zodiac. Until research supports a particular zodiac, individual astrologers will remain attached to their favored zodiac, and controversy will continue in the astrological world with some astrologers claiming that all the zodiacs work. In my opinion this isn't a tenable solution to the zodiac question.


Therese Hamilton
May 20, 2004



For deeper studies, read:

Raymond Mercier, ”Studies in the Medieval Conception of Precession”

in 'Archives Internationales d'Histoire des Sciences', (1976) 26:197-220 (part I), and (1977) 27:33-71 (part II)


Allen, Richard Hinckley, "Star Names and Their Meanings",  Kessinger Publishing (2003).


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