The Ujjain Observatory, located in the city of Ujjain, Madhya Pradesh, is believed to be one of the oldest observatories in the world, dating back to the 5th century BCE.

Aryabhata, a renowned mathematician and astronomer, is widely considered the father of Indian astronomy. He made significant contributions to the field, including the development of the Aryabhata system of astronomy.

Aryabhata proposed the heliocentric model of the solar system, where the Earth and other planets revolve around the Sun. This concept was revolutionary at the time and contradicted the prevailing geocentric model.

Varahamihira's Brihat Samhita is a comprehensive treatise that encompasses various branches of knowledge, including astronomy. It covers topics such as planetary positions, eclipses, and astrological predictions.

Brahmagupta is credited with developing the concept of the zero and introducing it to the world. He also made significant contributions to astronomy, including the formulation of the Brahmagupta equation.

The armillary sphere was an important astronomical instrument used by Indian astronomers to measure the positions of celestial bodies and study their movements.

Bhaskara II calculated the value of pi (π) to an accuracy of four decimal places, which was a remarkable achievement in ancient times.

Maharaja Jai Singh II built five Jantar Mantars, astronomical observatories, in different cities across India, including Delhi. These observatories were equipped with various instruments for astronomical observations.

Varahamihira is credited with developing the Surya Siddhanta, an influential astronomical text that provided detailed information about planetary positions, eclipses, and other astronomical phenomena.

The Man Mandir Observatory, located in Varanasi, India, was built by Maharaja Man Singh I in the 16th century. It is known for its unique architectural design and the instruments it housed for astronomical observations.

Aryabhata proposed the idea that the Earth rotates on its own axis, contradicting the prevailing belief that the Earth was stationary.

Bhaskara II's Lilavati is a mathematical and astronomical treatise that covers various topics, including arithmetic, geometry, and astronomy. It contains significant contributions to the field of astronomy.

Varahamihira's Panchasiddhantika is a treatise that compares five different astronomical systems known at the time. It provides insights into the astronomical knowledge and practices of ancient India.

The Jantar Mantar in Jaipur, India, is one of the five astronomical observatories built by Maharaja Jai Singh II. It is known for its unique instruments and architectural design.