The zodiac according to Indian Astrology comprises of 360 degrees. There are 27 Nakshatras or constellations in it. Therefore, the value of each constellation is 13 degrees and 20 minutes when measured from the fixed initial point. Each Nakshtra is divided in padas or charan, every Nakshtra has 4 padas or charan. These 27 Nakshatras (constellations) complete the entire circle of 360 degrees of the zodiac.
The concept of Nakshatras is used in Vedic Astrology for accurate predictions and astrological analysis. Janamanakshtra is the Nakshatra in which the Natal Moon is placed at the time of birth. Janamnakstra gives an insights to one's thinking patterns, characterstics of the person and calculating the dasha period. As per our Hindu Mythology, Moon had married all the 27 daughters of King Dakshan, who are the 27 nakshatras in the sky. But, Moon loved to spend time with only one his beloved queen Rohini Nakshtara, which is also the exaltation point for Moon. Other wives (Nakshtras) complained to their father (King Dakshan), repeated requested to Moon by King was unable to change Moon's nature, finally King Dakshan got angry and cursed Moon, causing it to wane in size.
Moon started diminishing in size. Since the consequences of this was not good, all Devas intervened and requested King Dakshan to withdraw the curse. King was given assurance that Moon will visit all his wives, since the curse cannot be revoked completely, King Dakshan said Moon will regained his strength for half a month, that is the reason Moon transits all 27 nakshtras in a month, completing the zodiac orbit causing Amavasya and Poornima by waxing and waning in size.