Hindu astrology is based on the interpretation of nakshatras (constellations), "rasis" (astrological signs) and Navagraha (the astrological planets). Planetary combinations and their indications are based on strength, nature, aspect, and avastha (state). Hindu astrology requires the identification of yogas and their application in accordance with established principles. Although yogas are based on fundamental principles described in standard texts, not all texts cover all possible planetary combinations and associations, and texts have different interpretations of a given yoga. Certain yogas described in the texts cannot occur; these relate to Mercury and Venus vis-à-vis the Sun. Mercury never goes beyond 28 degrees in front of or behind the Sun, and Venus never goes beyond 47 degrees. Saraswati yoga is common and auspicious. Yogas are generally classified as Chandra (Moon), Surya (Sun), Nabhasa (celestial), Raja, Dhana, or Darida. Their common factor is the relative strength of the planets and their houses by ownership, occupation or aspect. Janardan Harji, in the fourth chapter of his "Mansagari", assigns certain outcomes to certain combinations. Yoga results are indicated by the circumstances of birth and the course of a person's life, from birth to death. According to "Saravali", the planets amplify a person's fate. Hindu astrologers have attempted to enumerate all possible yogas, with varied results.