Brahmasphutasiddhanta (Complete Sanskrit Text)

By accepting the movement of the Earth and the stillness of the planetary revolutions—the view that "the Earth rotates on its own axis in the duration of a day and night," which is considered by Āryabhaṭa—the statement "the rotation is the main flaw" is made. Elsewhere, Brahmagupta mentions many exaggerated statements made out of stubbornness or bias:

The clarity that Āryabhaṭa claimed for his own mathematics,
that has been proven to be lack of clarity due to the discrepancies in eclipses and other phenomena.
Because Āryabhaṭa does not even know one [correct method] of mathematics, time, or the sphere,
I have not separately enumerated their faults.
Since the number of errors in Āryabhaṭa cannot be counted,
this is just an outline; the intelligent should add the rest.

Brahmagupta, who was himself an observer of planetary eclipses, sets forth in his book, with bold statements, many specific methods for calculating planets and observational techniques to test the truth or falsehood of mathematics:

Having determined the mean position, the difference between that and the other day is the motion.
By the Rule of Three, [the daily] motion, [and] the calculation of the planetary cycle of a kalpa an aeon.
If the siddhāntas treatises are different, even the equinoxes are equal only by difference.
The one whose sunrise at the equinox is [aligned] in the east, that is the correct one.

From this, it is understood from the available astronomical treatises that Brahmagupta was the first to compose a definitive, highly specific, and analytical Siddhānta text deeply committed to reality. In the opening of his Gaṇitādhyāya of the Siddhāntaśiromaṇi, Bhāskarācārya bows to Brahmagupta, calling him "the crest-jewel of the circle of mathematicians, the son of Jishnu, whose work triumphs." Although he mentions Brahmagupta's opinions in many places, his statement, "as the tradition accepted by Brahmagupta is accepted here in this book," indicates that he composed his book following Brahmagupta's tradition. It is known from the Brahmasphuṭasiddhānta that Brahmagupta did not observe the precession of the equinoxes (ayanacalanā). Rather, it seems that the observation of the precession of the equinoxes was refuted:

The day and night lengths change according to the movement of the Sun at the end of the Mithuna Gemini sign,
but the ayana solstice pair is stable due to the lack of ayana precession.

That Varāhamihira was doubtful regarding the precession of the equinoxes is known from his statement, "Indeed, there was a time when this was stated in the ancient scriptures." At that time, the equinox was at the beginning of the Ashvini constellation, and the star-counting method beginning with Ashvini became current; that same system has continued from Brahmagupta until today.