Nakshatra, Rasi and Graha
Vedic Astrology is heavily based on Nakshatras or lunar constellations. Each Nakshatra is linked to a graha(planet). A group of Nakshatras forms each sign of the Zodiac (Rasi).
The Zodiac is a circle categorized into 360 degrees and each degree into 60 min and each min into 60 seconds. The whole zodiac belt is divided into 12 Rasis and each rasi is of 30 degrees.
1-Aries, 2-Taurus, 3-Gemini, 4-Cancer, 5-Leo, 6-Virgo, 7-Libra, 8-Scorpio, 9-Sagittarius, 10-Capricorn, 11-Aquarius, 12-Pisces
There are 27 Nakshatras spread along the zodiac belt. For the mathematical purpose, the span of each nakshatra is further divided into 4 padas. Every rasi has 2 and ¼ Nakshatra or nine nakshatra padas. Hence the distribution of Nakshatra in rasi is as in the chart below: