The Sun Treatise

...arc-minutes, which must have occurred 60 years after Brahmagupta. In this way, this later limit original: अपरा सीमा (Apara Sima); the upper bound of the date range becomes 628 + 60 = 718 AD.

In this manner, it can be concluded that the composition of the Surya-Siddhanta took place between 400 AD and 725 AD. Bentley and Burgess also determined the timing of the Surya-Siddhanta in a similar way by comparing the polar longitudes original: ध्रुवाङ्क (Dhruvamka); the position of a star measured along the ecliptic of the lunar mansions given in the Surya-Siddhanta with coordinates established by modern astronomy. However, that does not seem entirely correct, because the same types of errors in observation original: वेध (Vedha) that the author of the Surya-Siddhanta might have made, Brahmagupta and others would have likely made as well. Thus, the earlier limit original: परा सीमा (Para Sima) of the composition period could be extended further back. However, the later limit could reach as far as 1100 AD, as Bentley has demonstrated.

The matter of the precession of the equinoxes original: अयन-चलन (Ayana-chalana); the slow wobbling of Earth's axis that changes the positions of stars over time also supports Bentley’s view. During the time of Bhaskaracharya, the rate of precession mentioned in the Surya-Siddhanta was not as high as it is in the current version of the Surya-Siddhanta. This suggests that the revision of the rate of precession was carried out after Bhaskaracharya’s time. However, Bhaskaracharya’s era is known to be 1150 AD.

The Author of the Surya-Siddhanta—It has already been shown that the celestial coordinates in the Surya-Siddhanta do not match those of the Greek astronomers Hipparchus, Ptolemy, or astronomers from other Western countries. Therefore, this book was not written based on their observations. Its lineage original: परम्परा (Parampara) is attributed to Vivasvan, that is, the Sun God (see the Chapter on Mean Motions original: मध्यमाधिकार (Madhyamadhikara), verses 8-9), just as the lineage of the path of Yoga is described in the Bhagavad Gita (see Bhagavad Gita, Chapter 4, Verses 1-2). Mayasura The figure to whom the Sun God reveals the science in the text is not a foreigner. Being a resident of India, he acquired this knowledge, and from him, the sages also learned it later. This appears to be the secret behind the legend provided in the Surya-Siddhanta. The story regarding the Sun God being born in the city of Romaka Often associated with the West or Rome/Alexandria in ancient Indian texts due to a curse from Brahma is fabricated and is found in only one or two manuscripts.