Prachi Grah Shanti Yagna is done to remove the negative effects of nine celestial bodies which are referred to as Navgrahas in Vedic Astrology. 9 Celestial bodies include the sun, moon, mars, mercury, Jupiter, Venus, Saturn, Rahu and Ketu. According to astrology, movement or change in the position of Graha can change a person's life like various doshas.
To perform this puja, one must perform a hawan/homam, while chanting the Navagraha puja mantra. During the puja, people light up incense sticks and diyas with complete devotion.