Vedic astrology and Western astrology represent two different systems of looking at the stars. It is important to understand the differences between the two systems and how they developed. Here we will include a general discussion of the difference between the systems along with the definition of some important terms relative to the subject. Vedic astrology uses fixed stars, based on an ancient system that finds its roots in the Vedic scriptures and the words of the sages. Western astrology uses a moveable zodiac and is not based on the Vedas.
The fixed zodiac is also known as the sidereal zodiac. The moveable zodiac is also known as the tropical zodiac. The astronomical phenomenon that gives rise to the two systems is called the Precession of Equinoxes. This refers to the movement of the Earth on its axis. The Earth moves on its axis like a spinning top which means as it rotates, the axis also moves. The axis moves in a circle of 47° around the celestial equator relative to the ecliptic. This means that the intersection of the celestial equator and the ecliptic changes over time. The point of intersection is known as the Vernal Equinoctial point or the first point of Aries. This point will continue to move westward by 50.26 seconds every year. It will take 72 years for the Sun to move 1 degree westward. Eventually, the Sun will rise in different constellations from its current position. Though the Sun moves into a different sign each month, it rises in the same constellation for about 2610 years. This Precession of Equinoxes takes 28,500 years to complete and come back to its original point. The current North star is Polaris, but in time it will be others.The fixed zodiac system uses a fixed star as the basis of the first degree of Aries. The movable system uses the vernal equinox point as its basis for the first point of Aries. As discussed above the vernal equinoctial point moves westward by 50.26 seconds every year, thus an adjustment needs to be made for this time difference. The difference between these two points is called AYANAMSHA. The fixed Vedic system is called Niryana and the moveable system is known as Sayana. The time difference between these two systems can be found online and the calculation is made to adjust for the movable horoscope. The below image should make this concept of Precession of Equinoxes a little bit more clear
Earth’s Measure is the Golden Key to Precession
By Iona Miller, 2009
The Vedic system does not require correction for the changing vernal equinoctial point as it uses a fixed star in Revati as its basis. This allows for calculations and predictions based on the ancient Vedic scriptures without adulteration.
Some important terms relative to the movements of the Sun and Earth are below.
- Sidereal Day- The rotation of the Earth relative to a fixed star. The time for this orbit is 23 hours, 56 minutes, and 4.09 seconds.
- Mean Solar Day- The rotation of the Earth relative to the Sun. This is 24 hours.
- Sidereal Year- The duration of time for the Earth to orbit around a fixed star. This is 365 days, 6 hours, 9 minutes, and 9.5 seconds.
- Tropical Year-The duration of time for the Earth to orbit around the Sun. This is 365 days, 5 hours, 48 minutes, and 46 seconds.