Classical Indian astronomy documented in literature spans the Maurya (Vedanga Jyotisha, c. 5th century BCE) to the Mughal (such as the 16th century Kerala school) periods. The first named authors writing treatises on astronomy emerge from the 5th century, the date when the classical period of Indian astronomy can be said to begin. Besides the theories of Aryabhata in the "Aryabhatiya" and the lost "Arya-siddhānta", we find the "Pancha-Siddhāntika" of Varahamihira. The astronomy and the astrology of ancient India (Jyotisha) is based upon sidereal calculations, although a tropical system was also used in a few cases.