TROPICAL (SAYANA), SIDEREAL (NIRAYANA) LONGITUDES & AYANAMSA:
Vedic Astrology follows the Nirayana or the sidereal zodiac; whereas the Western Astrology follows the Sayana or the tropical zodiac.
“Sayana” zodiac system makes calculations and predictions based on the present position of the planets from a zodiacal point of view.
In the Nirayana system, planetary positions are as seen from Earth by taking into account the tilting of North pole by making corrections accordingly. The word Nirayana is derived from nir + ayana, which means without ayanamsa
According to scientific calculations, present shift started in the year 285 AD, i.e. at that time the North Pole was perfectly vertical at 90 degrees.
Western scientists are officially “credited” with the “discovery” of accurate shifting of earth’s equinox towards the end of the 19th century. They found it to be 50″. Varahamihira, the famous astrologer in the court of Vikramaditya in the year 57BC, clearly mentioned in his work Pancha Siddhantika, based on our ancient Siddhantas, that the ayanamsa is 50.32 seconds, which is considered to be the most accurate one.
Difference between the Sayana longitudes and the Nirayana longitudes of Planets is called “Ayanamsa” or precision. This Ayanamsa difference is the exactly calculated shift or inclination of the equinox.
Ayanamsa = Sayana Longitude – Nirayana Longitude
From the longitude position of planets in the Zodiac at this moment, when this Ayanamsa is deducted, we get the correct longitude of the planets as applicable to our position on earth.
PROBLEM:
1. Calculate Nirayana Longitude for Sun, if Sayana Longitude is Aries 28[SUP]o[/SUP]15’ and Ayanamsa is 25[SUP]o.[/SUP]
Sayana Longitude = 0[SUP]s[/SUP]28[SUP]o[/SUP]15’
Ayanamsa = 25[SUP]o[/SUP]
Nirayana Longitude = Sayana Longitude – Ayanamsa
0[SUP]s[/SUP]28[SUP]o[/SUP]15’ – 25[SUP]o[/SUP]
Nirayana Longitude/Sun = 0[SUP]s[/SUP]03[SUP]o[/SUP]15’.
2. Calculate approximate value of Ayanamsa for year 2013 AD.
It was observed that there is a tilt of North Pole of the Earth, measured to be slightly over 23[SUP]o[/SUP], as a result there is a shift in the equinox. It was stated that in the year 285 AD, the North Pole was perfectly at 90[SUP]o[/SUP] or the shift in equinox was 0 and it was ascertained that the shift in equinox, called Ayanamsa, is at 50[SUP]o[/SUP]32’. So to find the value of ayanamsa for 2013 AD, we should find the time elapsed since 285 AD to 2013, which is 1728 Years. As the shift is 50.32” for each year, for 1728 years it comes to 24[SUP]o[/SUP]09’.
Therefore, the approximate value of Ayanamsa for 2013 is 24[SUP]o[/SUP]09’.