There are 3 main types of the Zodiacs:
I. the Tropical Zodiac; II. the Sidereal Zodiac; III. The Zodiac based on the real Constellations.
Inside: the Tropical Zodiac
In the middle: the Sidereal Zodiac
In the outermost zone: the Zodiac of the
I. the Tropical Zodiac
The starting point of the tropical zodiac is based on the position of vernal equinox of the northern hemisphere (i.e. the intersection of the ecliptic with the celestial equator). There are 12 tropical signs – 12 sectors or zones along the Ecliptic and each of these 12 has an angular length of 30 arc degrees. Thus, this type of Zodiac is equisectorial. The tropical system remains prevalent in western astrology.
(We remark that
A. In analogy of the Tropical
one, we can create the Draconic zodiac too; in this case we must start the
first of the 12 equisectorial zodiac signs with the Ascending Lunar Node (Caput
Draconis, Dragon Head) instead of Vernal Equinox Point. On the analogy of the
tropical signs, we attribute the tropical qualities to the Draconic segments,
the first will have Aries quality, the second that of Taurus, the third that of
Gemini and so on.
B. It is possible to consider an Anomalistic Zodiac, if we are focusing on the Lunar Apsides, namely on the Perigee and Apogee Points of the Moon which are from this approach in analogy with the Ascending and Descending Lunar Nodes (Cauda and Caput Draconis.)
II. the Sidereal Zodiac
Because of the precession of the equinox, the Tropical system do not remain fixed relative to the Sidereal one but drift apart by about 1.4 arc degrees per century (0 d 0 m 50 s per year).
The ancient Hindu astrology is based on this sidereal or visible zodiac, accounting for the shift of the equinoxes by a correction called ayanamsa (ayanamsha). During the 20th century, after the examinations of Cyril Fagan, many western astrologists have shown interest in the sidereal system. The sidereal zodiac is called Jyotish or Jyotisha by the Indian astrologers; its other name is Nirayana).
The Lahiri ayanamsha is the most known one in India, it was exactly 23 d 51 m 11 s for epoch 2000 A.D., but the western siderealists consider rather the ayanamsa by Fagan and Bradley which was 24 d 44 m 12 s for epoch 2000 A.D. (Some extremities for epoch 2000: the ’smallest ayanamsa’ was calculated by Raman - 22 d 24 m 25 s – and the ’greatest’ by Larry Ely – 28 d 00 m 13 s.)
In a nutshell: like the Tropical ones, there are 12 sidereal signs along the Ecliptic, each having an angular length of 30 arc degrees. Thus this type of Zodiac is equisectorial too. The essential difference between the tropical and the sidereal zodiac is that the starting point of the Sidereal one is NOT SIMPLY the Vernal Equinox Point but you must SUBSTRACT the considered ayanamsha from the tropical (ecliptical) longitude of the Vernal Point (V.P. represents always the 0 degree of the tropical Aries.)
III. the Zodiac of the real Constellations
The most important difference from A. and B. (Tropical and Sidereal Zodiac) that this Zodiac – the Zodiac of the real/true Constellations - are NOT equisectorial, each of its 12 segments/sectors has a different angular size.
To understand correctly these 3 types of the Zodiacs, please note:
- Within the Tropical System the starting point is EXACT - it is always the Vernal Point of the Northern Hemisphere - and the 12 segments/signs can by EXACTLY MEASURED too (each of them is exactly 30 arc degrees.
- Within the Sidereal system the consideration of the starting point is SUBJECTIVE (thus there are a lot of ayanamshas), BUT the 12 segments/signs can be EXACTLY MEASURED along the Ecliptic (each of them is exactly 30 arc degrees too.)
- Within the system of the true (or real) Constellations
the consideration of a starting point is SUBJECTIVE AND the determination of the angular size of
the 12 sectors is SUBJECTIVE TOO.
To determine the starting (and ending) points of the real Constellations along the Ecliptic (and thus to consider the Zodiac of the true Constellations) we must choose some Marker Stars - or Fiducial Stars – and this is inevitably a subjective act; some people can accept it, others can deny it having their own solutions… (Despite these indisputable facts, it is not a senseless thing to try to divide the true Constellations to obtain this third type zodiac – Inner Sky Electrum Innovative Astrology Software – introducing the concept of the ’dynamic arc degrees’ - can represent several methods of the division in the chart wheels.)
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It remained still to throw light on the correct use of two important astrological terms: SIGNS and CONSTELLATIONS. Unfortunately there are many websites that misuse these terms, if you would like use them correctly, please note:
- The 12 equal segments of the Tropical Zodiac are Tropical SIGNS or Zodiac(al) SIGNS /and NOT Tropical Constellations or Zodiac(al) Constellations/;
- The 12 equal segments of the Sidereal Zodiac are Sidereal SIGNS or Zodiac(al) SIGNS /and NOT Sidereal Constellations or Zodiac(al) Constellations/;
- The 12 unequal sectors of the Zodiac of the real Constellations are CONSTELLATONS or Zodiac(al) CONSTELLATIONS /and NOT Signs or Zodiac(al) Signs./
Samples - Several Zodiacs
(All Samples were created by ISE Program, the 'Zodiac Expert')
1. Inside: Tropical Zodiac; in the middle: Draconic Zodiac; in the outermost zone: true Constellations /illustrations by Hevelius/
2. /Hellenistic/Tropical Zodiac; Chinese Tropical Zodiac; true Constellations /illustrations by Grotius/
3. /Hellenistic/ Tropical Zodiac; Oriental /Scythian/ Tropical Zodiac; Constellations /illustrations by As-Sufi/
4. Tropical Zodiac; Zodiac of the real /unequal/ Constellations; real Constellations sectors
Addendum - the Lunar Zodiac or the Lunar Mansions
The Lunar Mansion are segments of the Ecliptic (often called a station, or house) through which the moon moves in its orbit around the Earth. In general, the zodiac is divided into 27 or 28 segments by these systems, and like the Solar Zodiac, they can be considered
- Within the tropical frame (Tropical Lunar Mansions, starting with the Vernal Equinox Point);
- Within the sidereal frame (Sidereal Lunar Mansions, with a choosen ayanamsa);
- Within the frame of the real constellations (Lunar Mansions based on the 'Fixed Stars')
Let's view some widely known Lunar Mansion Systems as examples! (The Lunar Mansion systems are in the middle of the charts.)
1. Arabic Tropical Lunar Mansions (Manazil, with equal sectors)
2. Scythian Tropical Lunar Mansions (with unequal sectors)
3. Indian Sidereal Lunar Mansions (Nakshatra, with equal sectors)
4. Chinese Lunar Mansions based on 'Fixed Stars' (starting with Spica) (Xiu, with unequal sectors)
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© MdeS, 2011.