ANCIENT INDIAN OBSERVATORY JANTAR MANTAR DELHI,

Varahamihira’s main work is the book Pañcasiddhāntikā (or Pancha-Siddhantika, “[Treatise] on the Five [Astronomical] Canons) dated ca. 575 CE gives us information about older Indian texts which are now lost. The work is a treatise on mathematical astronomy and it summarises five earlier astronomical treatises, namely the Surya Siddhanta, Romaka Siddhanta, Paulisa Siddhanta, Vasishtha Siddhanta and Paitamaha Siddhantas. It is a compendium of native Indian as well as Hellenistic astronomy (including Greek, Egyptian and Roman elements).

The 11th century Arabian scholar Alberuni also described the details of “The Five Astronomical Canons”:
the Indianshave 5 Siddhāntas:

Sūrya-Siddhānta, ie. the Siddhānta of the Sun, composed by Lāṭa,
Vasishtha-siddhānta, so called from one of the stars of the Great Bear, composed by Vishnucandra,
Pulisa-siddhānta, so called from Paulisa, the Greek, from the city of Saintra, which is supposed to be Alexandria, composed by Pulisa.
Romaka-siddhānta, so called from the Rūm, ie. the subjects of the Roman Empire, composed by Śrīsheṇa.
Brahma-siddhānta, so called from Brahman, composed by Brahmagupta, the son of Jishṇu, from the town of Bhillamāla between Multān and Anhilwāra, 16 yojanas from the latter place.”
ANCIENT INDIAN OBSERVATORY JANTAR MANTAR DELHI,