Astrology Blog
The Three Zodiacs in Astrology
Tropical, Sidereal, Constellational
Published March 2026
How are the signs distributed in the sky? How do we track the placements of planets in their cycles around the Sun?
There are three main systems used in astrology:
- The Tropical Zodiac begins with the sign of ARIES on the March Equinox (around March 20).
- The Sidereal Zodiac begins with the sign of ARIES in the backdrop of fixed stars (today around April 15, but this changes over time)
- The Constellational Zodiac has same starting point as the Sidereal, but each sign is not 30 degrees equal, depending on the various sizes of constellations.
The TROPICAL ZODIAC
(Also simplistically referred to as Western Astrology, but in fact originates from the Middle East and is practiced worldwide).
The Tropical zodiac is fixed into space and places the astrological signs based on the EQUINOXES and SOLSTICES: the meeting and separating points between the Celestial Equator and the Path of the Sun (Ecliptic). See illustration 1.
- The Celestial Equator: the equator of the earth extended into space (Blue plane on Illustration 1).
- The Ecliptic, the Path of the Sun as we see it from earth (Yellow plane on Illustration 1)
- The two planes have a 23.5 degrees tilt between them.
- It takes one year for the Sun to complete a full 360 degree cycle – the Sun path is the foundation of our Gregorian calendar (365 days in a year)
- When the Sun is at the meeting point between the two planes, it marks the Equinoxes (March 20 & September 22).
- When the Sun is at its farthest distance from the celestial equator, it marks the Solstices (June 20 & December 21).
- In the Tropical Zodiac, Equinoxes and Solstices mark the beginning of the four Cardinal Signs: Aries, Libra, and Cancer, Capricorn.
Illustration 1 – The Celestial Equator is 23.5 degrees from the Ecliptic
From the four points (Equinox/Solstice), marking the Cardinal signs, the path of the Sun is divided into 12 equal parts: these are THE SIGNS.
- The 360 degree path of the Sun is split into 12 equal signs of 30 degrees each.
- Signs are a simple division of the Sun path into twelve parts.
- The names of the signs (Aries to Pisces) are derived from the constellation names that are in the backdrop of the Sun (See illustration 2).
As seen from earth, the Sun completing its cycle around us (Earth) passes in the backdrop of stars belonging to 12 to 13 constellations.
These constellations are different in size. For example, the constellation of Virgo is approximately 44 degrees long, whereas the constellation of Aries is only about 23 degrees long.
Confusing: Astrological signs are different from constellations, even though they share the same names.
Remember: Signs are 30 degrees equal, while Constellations each have different sizes.
Illustration 2 – A flat map of constellations, with markings for the Sun’s yearly path.
The constellations that the Sun travels through as we see it from Earth.
Maurice editing of the marking of the Scorpio constellation to match the astrological point of view.
While constellation names are used for the signs, they are not the same thing.
The Sun stays about 30 days in each sign, since it moves approximately 1 degree per day.
This pattern is fixed and does not change over time, therefore the dates for each sign do not change over time.
Critics of Astrology are confused
Scientists and critics claim that the dates of our signs are wrong because the Sun is not in the constellation of Aries on March 20. They confuse signs with constellations, showing they often lack fundamental understanding of astrology. It reflects their bias and prejudice. Their argument about the Sun travelling in the constellations refers to the Constellational Zodiac, not the Tropical one (see Illustration 6 below).
Confusion about a 13th sign – Ophiucus
For similar reasons, scientists and critics periodically claim that there are 13 signs rather than 12 signs. The reason is that on its yearly path, the Sun crosses one star in the constellation of Ophiucus – the name of that faint star is Yed Prior or C-Oph (see Illustration 3).
Because Ophiucus is close to the constellation of Scorpio, they claim that the Sun spends more time in the constellation of Ophiucus than the constellation of Scorpio. This again stems from mixing signs with constellations, likely with biased intent to discredit astrology with bad faith arguments. (See Illustration 3 and 6)
Illustration 3 – (Graphic from Stellarium)
The constellations of Scorpio and Ophiucus overlapping South and North of the Ecliptic. Critics of astrology claim that the Sun spends more time through Ophiucus than it does through Scorpio, which is arbitrary, but they also confuse signs with constellations.
Here is an example of a typical bad faith misrepresentation of Astrology in an Astronomy publication mish-mashing signs with constellations:
“Astrology suggests that each sign of the zodiac fits neatly into a 30-degree slice of sky – which multiplied by 12 adds up to 360 degrees. In actuality, this is not the case, as the constellations vary a great deal in shape and size. For example, the Sun passes through the constellation Scorpio in just five days, but takes 38 days to pass through Taurus. This is one of the reasons astrological signs do not line up with the constellations of the zodiac.”
Reply: Educated astrologers know that signs are not constellations. The confusion stems from sharing the same name.
Are Signs in the Tropical Zodiac based on seasons?
Because signs are aligned with the Equinoxes and Solstices, there is a common assumption among astrologers that the signs relate to seasons in the northern hemisphere. However, since astrology works the same in both north and south hemisphere, and then on the Equator where seasons are different altogether, we may ask whether this assumption makes sense? Let’s examine the argument:
Wouldn’t Sagittarius better match the southern season leading to summer Solstice, with the increase of light and heat to the maximum amount of daylight in the southern hemisphere?
March Equinox: from Aries, Taurus, to Gemini: representing Spring season in the north where seeding, emergence (Aries), the blooming of flowers (Taurus), pollination (Gemini), and the birthing of animals (Aries) occurs in the northern hemisphere. These signs match well the northern seasons, however, this period is Autumn in the southern hemisphere where the light is dimming and weather gets colder. Can Taurus also reflect the storing of food in the southern season, in preparation for winter?
June Solstice: from Cancer, Leo, to Virgo: reflecting the peak of summer, the fruiting of trees (Leo), and the harvest of crops (Virgo) in the north. Yet, is shy and introverted Cancer, traditionally representing domestic life and intimacy, a good match for marking the exuberance of summer with the peak amount of daylight and heat? Wouldn’t Cancer better fit winter time temperament, retreat, hibernation, and gestating under cover, marking the start of the southern winter? Is water sign Cancer matching the start of the dry season on the Equator?
September Equinox: from Libra, Scorpio, to Sagittarius: associated with the northern dimming of light, falling leaves, and decay of nature (Scorpio). Animals mating ahead of winter (Libra and Scorpio season). However, does the sign of Sagittarius, naturally representing expansion, growth and migrations, accurately reflects the northern season where light is dimming to its darkest, shortest day? Wouldn’t Sagittarius better match the southern season leading to the summer Solstice, with the increase of light and heat to the maximum amount of daylight in the southern hemisphere?
December Solstice: from Capricorn, Aquarius, to Pisces: association with the northern winter, retreat, and colder winter months. Yet, is industrious and ambitious Capricorn a good match for hibernating winter time? Wouldn’t it match the maturation, coming to fruition of southern summer? Would Pisces better match the fishing season of late southern summer?
Signs may be similar to northern seasons rather than deriving from them. An important distinction.
We can see that the Sun’s position in the signs is an approximate match with northern seasons, yet with recurrent inconsistencies, putting the validity of this theory into doubt. While the signs’ sequence does reflect cycles, it may be similar to northern seasons rather than deriving from northern seasons.
From what we know, the meanings and classification of signs originated from Mesopotamia. The sequence and cyclical nature of signs seem to go beyond “cookie cutter” seasonal associations.
Are Signs Directional rather than Seasonal?
Astrologer and astronomy enthusiast Gemini Brett refers to the signs of the zodiac as Directional rather than seasonal. He purports that anywhere on the planet, north, south, and center, Aries points to the East, Cancer to the North, Libra to the West, and Capricorn to the South.
From Aries to Cancer season, the Sun moves from the Equator to maximum (23.5) North.
From Cancer to Libra season, the Sun switches from North, to begin its return to the South.
From Libra to Capricorn season, the Sun travels to reach the maximum (23.5) South.
From Capricorn to Aries season, the Sun switches direction from South, to begin returning North.
Illustration 4 – the Sun rising at different places during the year
Due East on the March and September Equinoxes.
23 degrees North of East on the June Solstice / 23 degrees South of East on the December Solstice
The SIDEREAL ZODIAC
The Sidereal zodiac finds its starting point according to the location of certain fixed stars, and from there, divides the path of the Sun into 12 equal parts that represent the signs. This zodiac originates from India, under the Sanskrit name Jyotish, or Vedic astrology, but is practiced by astrologers everywhere today.
- Currently, there is a 24 degree discrepancy between the Sidereal (drifting) and Tropical (fixed) zodiacs.
- There are different star references used to mark the starting point of the Sidereal zodiac. The main one is Spica. According to this system, the location of Spica represents the 0 LIBRA point – exactly opposite (180 degrees) from the start of the Aries point. It is referred to as the Chitra Paksha (Sanskrit for Spica marker).
- Spica is used as a reference because it is a bright star that is easy to find and right on the Ecliptic (path of the Sun).
- While Spica is used as the 0 Libra Point (Lahiri Ayanamsha), astronomically it is actually a star in the constellation of Virgo. This is another reminder of the distinction between signs and constellations, in both Tropical and Sidereal zodiacs.
- The position of stars, including Spica, moves 1 degree every 71.6 years – the reason is that the whole position of constellations and stars in the sky are subject to a phenomenon called the Precession of the Equinoxes: all stars in the sky drift 1 degree every 71.6 years, through the zodiac, taking 25,776 years to complete the 360 degree cycle. This cycle is called The Great Year.
- Therefore Spica, and the start of the Sidereal zodiac also drift 1 degree per 71.6 years. Today, the Sun reaches Spica appox. on October 16/17 – which is the 0 Libra point of the Sidereal zodiac. In approximately 72 years, the Sun will reach Spica a day later on October 17/18, and so forth.
- Currently, there is a 24 degree discrepancy between the Sidereal (drifting) and Tropical (fixed) zodiacs.
Practitioners of the Sidereal zodiac claim that it more accurately depicts the position of planets with constellations as they are in the sky, but this is fundamentally misleading since the Sidereal signs are also divided into 12 equal signs of 30 degrees each, and are not the same size as the constellations they are named after.
- Someone born on April 14, 2026 will have their Sun @ 0 degrees Aries in the Sidereal zodiac, compared to 24 degrees Aries in the Tropical zodiac.
- Each zodiac has its virtues and rationales and should be used separately as “two different languages.”
The CONSTELLATIONAL Zodiac
The constellational zodiac marks and divides signs according to the time the Sun actually passes in the backdrop of each constellation, according to their different sizes. Accordingly, the sign of Virgo would be about 44 degrees long, and the sign of Capricorn would be 28 degrees long, based on the actual size of these constellations.
However, the sky is not so clearly divided, making the boundaries between the constellations quite abstract and difficult to follow or agree upon. For example, the constellation of Scorpio and Ophiucus overlap over the path of the Sun, each on the opposite side of the Ecliptic (see illustration 3), making it impossible to firmly determine whether the Sun is in the sign of Scorpio or Ophiucus.
Similarly, the constellations of Capricorn and Aquarius overlap in some parts over the Ecliptic, making it impossible, if not arbitrary, to determine when would the Sun pass through one sign and move on to the next. (See illustration 5).
This is why the Constellational Zodiac is not widely used astrologically, and why the argument that we should determine the signs according to the placement of the constellations by the same names is not practical. However, it does keep the critics busy and astrologers rolling their eyes.
Illustration 5
The constellations of Capricorn and Aquarius are overlapping over the Ecliptic
The IAU mapping of Constellations
In 1930, the International Astronomers Union (IAU) defined the currently used size and names of constellations as depicted in Illustration 2. This map also decides how long the Sun spends in each constellation. This set of rules to lay out the sky is still an approximation since stars in the sky are not so neatly organized as scientists may try to make them be.
Different cultures had their own unique way to divide the sky in the course of time. Therefore, it is important to clarify that to follow the Constellational Zodiac is more precisely following the IAU version of the constellations.
The astrology software Solar Fire uses these constellation definitions in one of their chart wheel (Zodconst) to illustrate the outlines of the Tropical and Constellational zodiacs – Illustration 6 shows this comparison, set for the 2026 March Equinox.
Illustration 6 – Tropical versus Constellational Zodiacs (as defined by the IAU)
You notice that while the Sun is @ 0 Aries in the Tropical zodiac on the March Equinox, it travels the constellation of Pisces according to the IAU division. Pisces is a particularly large constellation that extends about 38 degrees.
Summary
I believe there are good reasons why the ancients who interpreted the sky came to divide signs into 12 equal parts/signs to reflect cycles of existence. Signs make more sense than constellations for astrological study of cycles. We must remember that different cultures across time grouped the stars differently from the constellations and meanings we now use. For example the Orion constellation was named by the ancient Greeks, while the Maori of New Zealand called that same grouping of stars the constellation of “The Canoe of Tamarereti.”
Why 12 signs?
The most common reference is that there are about 12 lunations per solar year (12.37 more accurately). Astrology relies on 12 equal signs in both the Tropical and Sidereal zodiacs. These twelve sections are where the Sun and planets are orbiting, reflecting astrological cycles of development.
For a visual study of the Three Zodiacs – View this video
Additional References
Take the full tutorial about Astronomy for Astrologers
The material covers the Precession of the Equinoxes, The ring of the North Stars, Retrograde planets, and much more
View details here
Video: New Perspectives on the 12 signs
© 2015 Maurice Fernandez – all rights reserved
No part of this article may be used without written consent of the author, unless credit and reference to this website are provided. With exception for listed credit owners.
The Three Zodiacs in Astrology
Tropical, Sidereal, Constellational
Published March 2026
How are the signs distributed in the sky? How do we track the placements of planets in their cycles around the Sun?
There are three main systems used in astrology:
- The Tropical Zodiac begins with the sign of ARIES on the March Equinox (around March 20).
- The Sidereal Zodiac begins with the sign of ARIES in the backdrop of fixed stars (today around April 15, but this changes over time)
- The Constellational Zodiac has same starting point as the Sidereal, but each sign is not 30 degrees equal, depending on the various sizes of constellations.
The TROPICAL ZODIAC
(Also simplistically referred to as Western Astrology, but in fact originates from the Middle East and is practiced worldwide).
The Tropical zodiac is fixed into space and places the astrological signs based on the EQUINOXES and SOLSTICES: the meeting and separating points between the Celestial Equator and the Path of the Sun (Ecliptic). See illustration 1.
- The Celestial Equator: the equator of the earth extended into space (Blue plane on Illustration 1).
- The Ecliptic, the Path of the Sun as we see it from earth (Yellow plane on Illustration 1)
- The two planes have a 23.5 degrees tilt between them.
- It takes one year for the Sun to complete a full 360 degree cycle – the Sun path is the foundation of our Gregorian calendar (365 days in a year)
- When the Sun is at the meeting point between the two planes, it marks the Equinoxes (March 20 & September 22).
- When the Sun is at its farthest distance from the celestial equator, it marks the Solstices (June 20 & December 21).
- In the Tropical Zodiac, Equinoxes and Solstices mark the beginning of the four Cardinal Signs: Aries, Libra, and Cancer, Capricorn.
Illustration 1 – The Celestial Equator is 23.5 degrees from the Ecliptic
From the four points (Equinox/Solstice), marking the Cardinal signs, the path of the Sun is divided into 12 equal parts: these are THE SIGNS.
- The 360 degree path of the Sun is split into 12 equal signs of 30 degrees each.
- Signs are a simple division of the Sun path into twelve parts.
- The names of the signs (Aries to Pisces) are derived from the constellation names that are in the backdrop of the Sun (See illustration 2).
As seen from earth, the Sun completing its cycle around us (Earth) passes in the backdrop of stars belonging to 12 to 13 constellations.
These constellations are different in size. For example, the constellation of Virgo is approximately 44 degrees long, whereas the constellation of Aries is only about 23 degrees long.
Confusing: Astrological signs are different from constellations, even though they share the same names.
Remember: Signs are 30 degrees equal, while Constellations each have different sizes.
Illustration 2 – A flat map of constellations, with markings for the Sun’s yearly path.
The constellations that the Sun travels through as we see it from Earth.
Maurice editing of the marking of the Scorpio constellation to match the astrological point of view.
While constellation names are used for the signs, they are not the same thing.
The Sun stays about 30 days in each sign, since it moves approximately 1 degree per day.
This pattern is fixed and does not change over time, therefore the dates for each sign do not change over time.
Critics of Astrology are confused
Scientists and critics claim that the dates of our signs are wrong because the Sun is not in the constellation of Aries on March 20. They confuse signs with constellations, showing they often lack fundamental understanding of astrology. It reflects their bias and prejudice. Their argument about the Sun travelling in the constellations refers to the Constellational Zodiac, not the Tropical one (see Illustration 6 below).
Confusion about a 13th sign – Ophiucus
For similar reasons, scientists and critics periodically claim that there are 13 signs rather than 12 signs. The reason is that on its yearly path, the Sun crosses one star in the constellation of Ophiucus – the name of that faint star is Yed Prior or C-Oph (see Illustration 3).
Because Ophiucus is close to the constellation of Scorpio, they claim that the Sun spends more time in the constellation of Ophiucus than the constellation of Scorpio. This again stems from mixing signs with constellations, likely with biased intent to discredit astrology with bad faith arguments. (See Illustration 3 and 6)
Illustration 3 – (Graphic from Stellarium)
The constellations of Scorpio and Ophiucus overlapping South and North of the Ecliptic. Critics of astrology claim that the Sun spends more time through Ophiucus than it does through Scorpio, which is arbitrary, but they also confuse signs with constellations.
Here is an example of a typical bad faith misrepresentation of Astrology in an Astronomy publication mish-mashing signs with constellations:
“Astrology suggests that each sign of the zodiac fits neatly into a 30-degree slice of sky – which multiplied by 12 adds up to 360 degrees. In actuality, this is not the case, as the constellations vary a great deal in shape and size. For example, the Sun passes through the constellation Scorpio in just five days, but takes 38 days to pass through Taurus. This is one of the reasons astrological signs do not line up with the constellations of the zodiac.”
Reply: Educated astrologers know that signs are not constellations. The confusion stems from sharing the same name.
Are Signs in the Tropical Zodiac based on seasons?
Because signs are aligned with the Equinoxes and Solstices, there is a common assumption among astrologers that the signs relate to seasons in the northern hemisphere. However, since astrology works the same in both north and south hemisphere, and then on the Equator where seasons are different altogether, we may ask whether this assumption makes sense? Let’s examine the argument:
Wouldn’t Sagittarius better match the southern season leading to summer Solstice, with the increase of light and heat to the maximum amount of daylight in the southern hemisphere?
March Equinox: from Aries, Taurus, to Gemini: representing Spring season in the north where seeding, emergence (Aries), the blooming of flowers (Taurus), pollination (Gemini), and the birthing of animals (Aries) occurs in the northern hemisphere. These signs match well the northern seasons, however, this period is Autumn in the southern hemisphere where the light is dimming and weather gets colder. Can Taurus also reflect the storing of food in the southern season, in preparation for winter?
June Solstice: from Cancer, Leo, to Virgo: reflecting the peak of summer, the fruiting of trees (Leo), and the harvest of crops (Virgo) in the north. Yet, is shy and introverted Cancer, traditionally representing domestic life and intimacy, a good match for marking the exuberance of summer with the peak amount of daylight and heat? Wouldn’t Cancer better fit winter time temperament, retreat, hibernation, and gestating under cover, marking the start of the southern winter? Is water sign Cancer matching the start of the dry season on the Equator?
September Equinox: from Libra, Scorpio, to Sagittarius: associated with the northern dimming of light, falling leaves, and decay of nature (Scorpio). Animals mating ahead of winter (Libra and Scorpio season). However, does the sign of Sagittarius, naturally representing expansion, growth and migrations, accurately reflects the northern season where light is dimming to its darkest, shortest day? Wouldn’t Sagittarius better match the southern season leading to the summer Solstice, with the increase of light and heat to the maximum amount of daylight in the southern hemisphere?
December Solstice: from Capricorn, Aquarius, to Pisces: association with the northern winter, retreat, and colder winter months. Yet, is industrious and ambitious Capricorn a good match for hibernating winter time? Wouldn’t it match the maturation, coming to fruition of southern summer? Would Pisces better match the fishing season of late southern summer?
Signs may be similar to northern seasons rather than deriving from them. An important distinction.
We can see that the Sun’s position in the signs is an approximate match with northern seasons, yet with recurrent inconsistencies, putting the validity of this theory into doubt. While the signs’ sequence does reflect cycles, it may be similar to northern seasons rather than deriving from northern seasons.
From what we know, the meanings and classification of signs originated from Mesopotamia. The sequence and cyclical nature of signs seem to go beyond “cookie cutter” seasonal associations.
Are Signs Directional rather than Seasonal?
Astrologer and astronomy enthusiast Gemini Brett refers to the signs of the zodiac as Directional rather than seasonal. He purports that anywhere on the planet, north, south, and center, Aries points to the East, Cancer to the North, Libra to the West, and Capricorn to the South.
From Aries to Cancer season, the Sun moves from the Equator to maximum (23.5) North.
From Cancer to Libra season, the Sun switches from North, to begin its return to the South.
From Libra to Capricorn season, the Sun travels to reach the maximum (23.5) South.
From Capricorn to Aries season, the Sun switches direction from South, to begin returning North.
Illustration 4 – the Sun rising at different places during the year
Due East on the March and September Equinoxes.
23 degrees North of East on the June Solstice / 23 degrees South of East on the December Solstice
The SIDEREAL ZODIAC
The Sidereal zodiac finds its starting point according to the location of certain fixed stars, and from there, divides the path of the Sun into 12 equal parts that represent the signs. This zodiac originates from India, under the Sanskrit name Jyotish, or Vedic astrology, but is practiced by astrologers everywhere today.
- Currently, there is a 24 degree discrepancy between the Sidereal (drifting) and Tropical (fixed) zodiacs.
- There are different star references used to mark the starting point of the Sidereal zodiac. The main one is Spica. According to this system, the location of Spica represents the 0 LIBRA point – exactly opposite (180 degrees) from the start of the Aries point. It is referred to as the Chitra Paksha (Sanskrit for Spica marker).
- Spica is used as a reference because it is a bright star that is easy to find and right on the Ecliptic (path of the Sun).
- While Spica is used as the 0 Libra Point (Lahiri Ayanamsha), astronomically it is actually a star in the constellation of Virgo. This is another reminder of the distinction between signs and constellations, in both Tropical and Sidereal zodiacs.
- The position of stars, including Spica, moves 1 degree every 71.6 years – the reason is that the whole position of constellations and stars in the sky are subject to a phenomenon called the Precession of the Equinoxes: all stars in the sky drift 1 degree every 71.6 years, through the zodiac, taking 25,776 years to complete the 360 degree cycle. This cycle is called The Great Year.
- Therefore Spica, and the start of the Sidereal zodiac also drift 1 degree per 71.6 years. Today, the Sun reaches Spica appox. on October 16/17 – which is the 0 Libra point of the Sidereal zodiac. In approximately 72 years, the Sun will reach Spica a day later on October 17/18, and so forth.
- Currently, there is a 24 degree discrepancy between the Sidereal (drifting) and Tropical (fixed) zodiacs.
Practitioners of the Sidereal zodiac claim that it more accurately depicts the position of planets with constellations as they are in the sky, but this is fundamentally misleading since the Sidereal signs are also divided into 12 equal signs of 30 degrees each, and are not the same size as the constellations they are named after.
- Someone born on April 14, 2026 will have their Sun @ 0 degrees Aries in the Sidereal zodiac, compared to 24 degrees Aries in the Tropical zodiac.
- Each zodiac has its virtues and rationales and should be used separately as “two different languages.”
The CONSTELLATIONAL Zodiac
The constellational zodiac marks and divides signs according to the time the Sun actually passes in the backdrop of each constellation, according to their different sizes. Accordingly, the sign of Virgo would be about 44 degrees long, and the sign of Capricorn would be 28 degrees long, based on the actual size of these constellations.
However, the sky is not so clearly divided, making the boundaries between the constellations quite abstract and difficult to follow or agree upon. For example, the constellation of Scorpio and Ophiucus overlap over the path of the Sun, each on the opposite side of the Ecliptic (see illustration 3), making it impossible to firmly determine whether the Sun is in the sign of Scorpio or Ophiucus.
Similarly, the constellations of Capricorn and Aquarius overlap in some parts over the Ecliptic, making it impossible, if not arbitrary, to determine when would the Sun pass through one sign and move on to the next. (See illustration 5).
This is why the Constellational Zodiac is not widely used astrologically, and why the argument that we should determine the signs according to the placement of the constellations by the same names is not practical. However, it does keep the critics busy and astrologers rolling their eyes.
Illustration 5
The constellations of Capricorn and Aquarius are overlapping over the Ecliptic
The IAU mapping of Constellations
In 1930, the International Astronomers Union (IAU) defined the currently used size and names of constellations as depicted in Illustration 2. This map also decides how long the Sun spends in each constellation. This set of rules to lay out the sky is still an approximation since stars in the sky are not so neatly organized as scientists may try to make them be.
Different cultures had their own unique way to divide the sky in the course of time. Therefore, it is important to clarify that to follow the Constellational Zodiac is more precisely following the IAU version of the constellations.
The astrology software Solar Fire uses these constellation definitions in one of their chart wheel (Zodconst) to illustrate the outlines of the Tropical and Constellational zodiacs – Illustration 6 shows this comparison, set for the 2026 March Equinox.
Illustration 6 – Tropical versus Constellational Zodiacs (as defined by the IAU)
You notice that while the Sun is @ 0 Aries in the Tropical zodiac on the March Equinox, it travels the constellation of Pisces according to the IAU division. Pisces is a particularly large constellation that extends about 38 degrees.
Summary
I believe there are good reasons why the ancients who interpreted the sky came to divide signs into 12 equal parts/signs to reflect cycles of existence. Signs make more sense than constellations for astrological study of cycles. We must remember that different cultures across time grouped the stars differently from the constellations and meanings we now use. For example the Orion constellation was named by the ancient Greeks, while the Maori of New Zealand called that same grouping of stars the constellation of “The Canoe of Tamarereti.”
Why 12 signs?
The most common reference is that there are about 12 lunations per solar year (12.37 more accurately). Astrology relies on 12 equal signs in both the Tropical and Sidereal zodiacs. These twelve sections are where the Sun and planets are orbiting, reflecting astrological cycles of development.
For a visual study of the Three Zodiacs – View this video
Additional References
Take the full tutorial about Astronomy for Astrologers
The material covers the Precession of the Equinoxes, The ring of the North Stars, Retrograde planets, and much more
View details here
Video: New Perspectives on the 12 signs
© 2015 Maurice Fernandez – all rights reserved
No part of this article may be used without written consent of the author, unless credit and reference to this website are provided. With exception for listed credit owners.
