Several types of lamps are used during the 'shodashopachara' puja, the 16 forms of Hindu worship in Tamil temples on festive occasions. This 'vel' (spear)-shaped lamp has 27 wick holders set atop, hence it is called the 'natshatra deepam' for the 27 constellations of the Tamil calendar.Such lamps are used only for specific occasions in temples when their symbolism becomes significant.
