Aryabhata is widely regarded as the father of Indian astronomy for his contributions to mathematics and astronomy, including the development of the Aryabhata system of astronomy.

Aryabhata's model of the solar system, known as the Aryabhata system, was the first comprehensive model to propose that the Earth rotates on its axis and that the planets orbit the Sun.

Aryabhata calculated the circumference of the Earth to be 24,835 miles, which is remarkably close to the modern value of 24,901 miles.

Varahamihira, a renowned Indian astronomer and astrologer, developed the concept of the zodiac and the system of 27 nakshatras, which are still used in Indian astrology today.

Bhaskara II wrote the influential treatise 'Surya Siddhanta', which became a standard text in astronomy for centuries and was used by astronomers in India and beyond.

Brahmagupta developed the method of interpolation in astronomy, which allowed astronomers to estimate the values of unknown quantities between two known values.

Aryabhata calculated the sidereal year, the time it takes for the Earth to complete one orbit around the Sun, to be 365.258756 days, which is very close to the modern value of 365.256363 days.

Aryabhata was the first astronomer to propose the concept of the precession of the equinoxes, the gradual shift in the position of the equinoxes over time.

Brahmagupta developed the 'Manduka' model, a theory of planetary motion that proposed that planets move in elliptical orbits around the Sun.

Aryabhata studied the lunar eclipse and calculated the Moon's shadow, providing valuable insights into the geometry of the Earth-Moon system.

Brahmagupta wrote the 'Grahaganita', a treatise that discussed planetary motion and eclipses, providing detailed calculations and methods for predicting these celestial events.

Varahamihira made significant contributions to the study of comets and meteors, providing detailed descriptions and observations of these celestial phenomena.

Varahamihira wrote the 'Pancasiddhantika', a treatise that compared five different astronomical systems, providing a comprehensive overview of the astronomical knowledge of his time.

Bhaskara II made significant contributions to the calculation of planetary positions and the development of astronomical tables, providing accurate data for astronomical calculations.

Bhaskara II wrote the 'Lilavati', a treatise that covered various topics in mathematics and astronomy, including the calculation of planetary positions and the construction of astronomical instruments.