Nilakantha Somayaji

Nilakantha Somayaji (1444-1544), from Kerala, was a major Indian mathematician and astronomer of the Kerala school of astronomy and mathematics and was a student of Damodara. Later, he lived in Tryambakeshwar. Among his many influential books, he wrote the comprehensive astronomical treatise Tantrasamgraha in 1501. He also wrote the Aryabhatiya Bhasya, which contains work on infinite series expansions, problems of algebra, spherical geometry, and many results of calculus. Grahapareeksakrama is a manual on making observations in astronomy based on instruments of the time.

The Tantrasamgraha 432 Sanskrit verses divided into 8 chapters, and it covers various aspects of Indian astronomy. It is based on the epicyclic and eccentric models of planetary motion.

Description of chapters below
Chapter 1: deal with the motions and longitudes of the planets.
Chapter 2: deal with the motions and longitudes of the planets.
Chapter 3: Treatise on shadow deal;
Various problems related with the sun's position on the celestial sphere;

The relationships of its ex-pressions in the three systems of coordinates namely ecliptic, equatorial and horizontal coordinates.

Chapter 4: on the lunar eclipse and On the solar eclipse
Chapter 5: treat various aspects of the eclipses of the sun and the moon
Chapter 6: vyatipata and deals with the complete deviation of the longitudes of the sun and the moon
Chapter 7: visibility computation discusses the rising and setting of the moon and planets
Chapter 8: elevation of the lunar cusps examines the size of the part of the moon which is illuminated by the sun and gives a graphical representation of it.

Courtesy:Internet