Indian astrology is centric to light, with relation to Sun, Moon, Stars and planets. It is about the study of stars, lights and their influence on human life. The Sun is the soul of our solar system, and together with Stars they radiate energy into space.
As said stars are self-illuminating like Sun, and stand in a permanent position in relation to each other. Though there are innumerable stars in the sky, Indian astrology takes into consideration only 27 star constellations to demarcate the zodiac circle.
Aswini, Bharani, Krittika, Rohini, Mrigasira, Aridra, Punarvasu, Pushyami, Aslesha, Maka, Purva Phalguni, Uttara Phalguni, Hasta, Chitra, Swati, Vishakha, Anuradha, Jyeshta, Moola, Poorvashada, Uttarashada, Sravana, Dhanishta, Satabhisha, Poorvabhadra, Uttarabhadra and Revati.
Moon is a satellite of earth. Moon and earth attract each other. Since Moon stands closest to earth, it has been given special importance in astrology. Moon requires 27 days, 7 hours and 47 minutes to revolve around the earth and 29 days and 13 hours to rotate on its axis. Since the rotation time is longer than the revolving time, we only see one side of the moon. Therefore, 14 ¾ days are daytime, and similar amount of time are nights. One lunar month is 29 ½ days, and a lunar year is 354 days.