Vedic astrology has two wings. The first one is concerned with 'mathematics' and 'astronomy'. It is known as "GANITA Jyotisha". Ganita in Sanskrit stands for 'Maths'.

A good astrologer has also to be a good mathematician and astronomer too. The ancient seers were astronomers, mathematicians as well as good yogic students. They could combine all the three to arrive at the correct picture of the heaven at any given moment at any place on this earth. They were also adept at marking the position of Grahas and the ascending sign at the exact degree of zodiac and represent it in a tabular form. Such tabulated form was called as the "JATAKA" or 'Kundali' or 'Horoscope' in English.

The other wing of astrology is called as the "PHALITA" or 'that which is proved'. The question rises as to what is proved? The answer to this is that the Karmic reaction cannot be wished away is proved in the chart.

'Surya Siddhanta' says that on this earth everyday 21600 lives are born and out of these 7200 are human births. Six hundred individuals are born in each sign of the zodiac each day. Hora is an hour and birth chart is prepared according to the hour of birth counted from Sunrise of the place of birth. 60 ghatikas are equal to a day and the number of Ghatikas and Vighatikas expired from sunrise marks the birth time.

In Vedic system a day consists of two parts. The "Ahas" or part of the day from Sunrise to Sunset and 'Rater' is the portion from Sunset to Sunrise of the next day. Thus an ahas + ratri are equal to a solar day.

The Vedic seers also noted that the zodiacal signs rising in the east do not have the same duration. So they tabulated the durations of each sign for each month of the year. From these tables the sign rising in the eastern horizon at the time of birth can easily be worked out.

In the Vedic method of casting, the position of ascendant and the planets are worked out as per the Sayana system or Moving zodiac and then the ayanamsa is deducted to arrive at the NIRYANA positions. Nirayana means Fixed.

The celestial equator is a great circle of the celestial sphere marked out by indefinite extension of the plane of terrestrial equator. The celestial equator and the ecliptic intercept each other at two points twice a year (north to south once and south to north the second) as Sun crosses the equator from north to south and viceversa. These two points are known as equinoctial points or the vernal equinox and the autumnal equinox. It has been observed and proved mathematically that each year at the time when the Sun reaches his equinoctial point of Aries, the position of the earth in reference to some fixed stars nearly 50-1/3 of space farther west than the earth was at the same equinoctial movement of the previous year.

The entire zodiac is subjected to this westward shift. This slight movement is known as the precession of Equinoxes. The zodiac, which reckons the first degree of Aries from the equinoctial point, which has a precession every year, is the movable zodiac or Sayana adopted by the western astrologers. It is also known as the zodiac of Signs. The fixed of Nirayana zodiac is the position arrived at after deducting the precession is also called zodiac of constellations of Nirayana zodiac.

The distance between the Hindu first point and the vernal equinox measured at an epoch is known as the "AYANAAMSA".