The oldest and most important treaitse of the post-Christian period on Indian Astronomy that has come down to us is the Surya Siddhanta consisting 14 chapters written in slokas. Alberuni says that Lata was the author of this work. According to the introductory verses Surya the sun-god revealed it to Asura Maya in the city of Romaka.

Surya Siddhanta of Varaha as given in his panca Siddantika are almost the same as those of the khandakhadyaka, it is clear that the old surya siddhanta was made up to date by Varaha by replacing the old constants in it by new ones from Aryabhata I's midnight system.

On astronomy.

The Siamese Manuscript holds the distinction of being the very first document relating to Indian Astronomy to reach Europe in a pristine form. Some fragments of Indian Astronomy had undoubtedly reached Europe in earlier times, but those tidbits were likely received in a highly altered form due to difficulties in translation, and the so-called cultural barrier. The Siamese Manuscript helped overcome this barrier by being a compendium of Indian astronomical knowledge in plain Siamese. The timing of the arrival of the manuscript in Europe was significant. After a couple hundred years the Renaissance was finally bearing fruit, and European intellectual prowess was at a peak. The deeper principles of Indian Astronomy, which had gone over the heads of the Greeks and the Arabs who first encountered them, could now be fully understood and appreciated for the first time by people outside India.

This is a new release of the original 1930 edition.