It is important to know what differentiates Vedic Astrology from the more well known Western Astrology.
Vedic Astrology or Jyotish (its Sanskrit name meaning Jyoti - Light and Isha - Lord) is based upon the Sidereal Zodiac as opposed to the Tropical Zodiac used in Western Astrology.
Although the Sidereal Zodiac was used by Western Astrologers like Ptolemy in the beginning, over the course of time a more symbolic zodiac was adopted which is astronomically inaccurate.
This difference between the two zodiacs is called the "Ayanamsha". The Ayanamsha takes into account the revolution of the earth's axis, a phenomenon in Astrology known as the "precession of the equinoxes".
To explain this in the simplest way possible the earth spins(wobbles to be more precise) on its own axis in a conical motion and takes approximately 25,800 years to complete one revolution. It means that every 2000 years the position of the vernal or spring equinox, which marks the beginning point of the first sign of the zodiac Aries is always changing and moving forwards in time.
Consequently the pole star also changes every few thousand years as seen in the figure below.
When a person born today has the Sun at 10 degrees in Aries using the Tropical Zodiac, in actual astronomical reality the Sun will be 23 degrees backwards placed in the sign of Pisces.
For example when the Sun used to move into Aries on the 21st of March at 200 A.D. today it will enter the sign of Aries around the 14th of April. When the Sun moved into the sign of Scorpio on the 22nd October at 200 A.D. today it will enter the sign of Scorpio around the 14th of November.
This the reason why the present day
SUN-SIGN ASTROLOGY is COMPLETELY WRONG.
It is a complete joke in more ways than one - it has very little to do with Real Astrology. It is time that it was erased from public/media consciousness.
The Sidereal Zodiac used in Vedic Astrology is astronomically accurate because it takes the shifting of the earth's axis into account when calculating the longitudes of the planets and constellations.
The Tropical Zodiac used in Western Astrology is a Symbolic Zodiac based upon the position of the planets and constellations as they were in the sky 2000 years ago.
The Sidereal zodiac is the real zodiac as it actually appears in the sky at any given moment.
In order to convert a Western (tropical) horoscope into a Vedic (sidereal) horoscope one needs to subtract the current ayanamsa from the Tropical longitudes of the planets and signs to get their Sidereal positions. Because the earth's axis is always changing its position the ayanamsa changes slightly every year.
In January 1, 1900 the ayanamsa was 22 degrees 27 minutes 59 seconds.
Today the ayanamsa is 23º 52' degrees.
There are various ayanamsas in use today. There are some disagreements on the actual measurement of the ayanamsa or longitudinal difference between the two zodiacs. The most popular and widely accepted ayanamsa in India was introduced by N.C. Lahiri. He calculates the precessional rate to be around 48 seconds per year.
Printed with the kind permission of OSFA – Orion School & Foundation For Astrology. The Home of Jyotish Ancient Indian Astrology.
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