There are 27 constellations in the zodiac each constellation measures 13. 20' or 13 degrees and 20 minutes. In Vedic astrology Constellations are very important in the delineation of horoscope and timing of events. The constellation in which one's natal Moon is posited indicates his personality types, it is like the Sun sign is in the western astrology, it decides the temperament, feeling capacity, intimate aspect of nature and personality of that individual. This is an important tool of self discovery and useful for all counseling and psychological purposes The constellations of Moons are important while matching different temperamental types and their possible interactions. Persons with different constellations have different types of nature and their possible interactions may be magical or disastrous depending upon the nature of constellations in which they are born. Marriage compatibility is totally based on the matching of constellations in Vedic Astrology and this can be used in all types of partnerships. The daily Moon constellation is also important in deciding the energy, potential and destiny of the day as each constellation has its own good or bad qualities and it colors the day and its potential actions as per its characteristics and qualities. The daily constellation of Moon is very important in the election of the right time for an auspicious event i.e. in the election of right time for marriage, starting of education, starting new business and for starting journey..
Though the constellations are primarily related to the Moon, but they are used in relation to the Sun and all other planets as well. The constellation in which one's ascendant rises unfolds important aspects of his life, his outer manifestations including his health and his character and spiritual potential can be judged by the constellation in which his Sun is posited. Thus constellations are very important in Vedic astrology as they provide deeper dimension to the astrological interpretation and a greater insight into the assessment of astrological horoscope . Each constellation is ruled by a planet and the ruler of the constellation in which a planet is posited also controls its effects . for example if Jupiter is posited in the constellation of Mars , it will have more Martial effect. Most of the systems of planetary periods like 120 years cycle of Vimshottari period are bases upon the Moon constellation and its planetary ruler for their calculations.
constellations are grouped in three categories Sattwa, Rajas and Tamas as per their primary qualities. Spirituality, purity, harmony and balance are the qualities of Sattwa category. Rajas shows high energetic activity and elite type of behavior. The basic qualities of Tamas are inertia, dullness, and darkness. The 27 constellations are divided into three groups of nine . The first nine constellations are rajasic in nature, second nine are tamasic and the final nine are sattwic. The names of these 27 constellations are as following
