On the tropical and equatorial and Fixed and disomy signs of the Zodiac

In the chapter entitled as above from Tetrabiblos, Claudius Ptolemy, the presumed founder of Horoscopic Astrology, tells us how and why the signs are divided into categories.
Each one of the 12 Zodiac Signs, Claudius Ptolemy believes that, occupy 30-degree arcs on the sky. Altogether we have 12 signs X 30 degrees = 360 degrees, a full circle. At points where the ecliptic intersects the celestial equator are the Equatorial Zodiac Signs: Aries and Libra. The Tropical zodiac Signs are at the summer solstice: Cancer and Capricorn at winter solstice.
Fixed features the author of the Tetrabiblos, 4 Signs that are post-tropical and post-equatorial ie: Taurus, Leo, Scorpio and Aquarius. They are called Fixed because of the humidity, heat, dryness and coldness that began to install firmly in the previous Signs.
Finally Disoma are the Signs that follow the fixed: Gemini, Virgo, Sagittarius, Pisces. They are named so because they lie between fixed and Equatorial or Tropical Zodiac Signs.
Modern Tropical Astrology left the category of the Fixed Signs the same and renamed Disoma to Variable. Equatorial merged with the tropical Zodiac Signs to the new class of the impulsive Signs.

In summary:
old name - new name - Zodiac signs
FIXED  -      FIXED -         Taurus, Leo, Scorpio, Aquarius
DISOMA  -   VARIABLES- Gemini, Virgo, Sagittarius, Pisces
TROPICAL - IMPULSIVE - Cancer, Capricorn
ISIMERINA  -IMPULSIVE -  Aries, Libra

Tropical Astrology accepted those supported by Claudius Ptolemy. They only changed some names but the substance, the method and the word remains the same.
Let's move on to the substance of the categories established by the Tropical Astrology to see whether they withstand scientific criticism.

Because of the precession of the Equinoxes, Heaven's dome has changed in relation to 100 AD So the signs of Aries and Libra that were Equatorial, today they have given their place in Pisces and Virgo. Because the path of the Sun crosses the celestial equator in Pisces and Virgo.
The summer solstice is now in Taurus and Winter solstice is in Sagittarius, so neither the Tropical Zodiacs are in the concept that was introduced by Ptolemy.
Hence the current category of impulsive left devoid of the cause that created it.
Needless to say that the two remaining categories did not apply because:
1. Aries is a fixed sign and not impulsive (as the next sign of Pisces)
2. Libra became fix from impulsive (as next of Virgo)
3. The Twins became fixed signs from variable (next of Taurus)
4. Capricorn became fixed from impulsive. (Next of Sagittarius)

Due to the motion of the Earth, the old classification is no longer valid. The Zodiac Constellations are 13 and the dates the Sun enters the signs have changed. This is no reason to stop dealing with astrology. Astrology just needs a new theory to adjusts its data to Astronomy's facts. Astrology Needs changes and winkle out from old dogmas.
"Astrology of the 13 signs of the Zodiac" is a new theory that removes the categorization of the constellations with the concept introduced by Claudius Ptolemy. It is putting Astrology in a new basis. News Signs have more autonomous features. The main criterion for Astrology is not to be opposed to Astronomy's data.
In my book "Astrology of the 13 signs of the Zodiac: Ophiuchus, the New sign of the zodiac circle" I'm answering a series of questions about the New Astrological Theory and explaining how to built the New Horoscope of the 13 Zodiac signs in a new more autonomous and scientific way.

Vasilis Kanatas
Physicist