The Siddhanta-siromani of Sri Bhaskara can be said to be an elaborate commentary on Surya-siddhanta and thus these two books are considered the stalwarts of ancient Hindu mathematical astronomy.
The fact that Sri Bimala Prasada Siddhanta Saraswati, also known as Srila Bhaktisiddhanta Sarasvati Thakura, was not only a great Gaudiya Vaisnava spiritual master but also one of history’s foremost astronomers, makes this book exceptionally pertinent for our understanding.
Edited by His Holiness Danavir Goswami. 835 pages, 8 color pages of illustrations, hardbound stitched binding, Bengali script of Sanksrit, Roman transliteration, English translations and glossaries.
Few notes about Surya Siddhanta
The first part of the Surya Siddhanta gives a rather lengthy description of how to calculate the Hindu day count. Given a particular date the Hindu day count is the number of days elapsed between the end of creation and the particular date given. Creation ended 1,955,880,000 years before midnight February 18, 3102 B.C. at Ujjayni, India. The Hindu day count is very similar to the Julian Day used by modern astronomers; the Julian Day is the number of days elapsed since noon January 1, 4713 B.C. at Greenwich, England. The Hindu calculation is overly complicated because it is based on a lunar calendar system and in order to determine the number of days one must first determine the number of lunar months.