The gnomon is a simple yet effective instrument used to measure time by observing the shadow cast by a vertical rod. It was widely used in ancient India for various purposes, including determining the time of day, solstices, and equinoxes.

The Jantar Mantar is a collection of large sundials constructed by Maharaja Jai Singh II in the 18th century. These sundials were used to measure time accurately and determine various astronomical parameters.

The Nakshatravalli is a Sanskrit text that provides detailed descriptions of the 27 lunar mansions (nakshatras) used in Indian astrology and astronomy. It includes information about their positions, characteristics, and associations with various deities.

The Surya Siddhanta is believed to have been composed in the 5th century CE. It is one of the most important and influential astronomical texts in Indian history, providing detailed mathematical models for calculating the positions of the Sun, Moon, and planets.

The armillary sphere is a complex instrument that allows astronomers to visualize and study the positions and movements of celestial bodies. It can be used to measure time, determine the positions of stars and planets, and predict eclipses.

The quadrant is a simple but effective instrument used to measure the altitude of celestial bodies above the horizon. It was widely used in ancient India for various astronomical observations.

The astrolabe is a versatile instrument that was used for various astronomical and navigational purposes. It can be used to calculate the time of day, determine the positions of celestial bodies, and navigate at sea by measuring the altitude of the Sun and stars.

The ancient Indian observatory at Ujjain was known as Vedhshala. It was a significant center for astronomical studies and observations in ancient India.

Aryabhata is known for his heliocentric model of the solar system, which placed the Sun at the center and the Earth and other planets revolving around it. This model was revolutionary for its time and challenged the prevailing geocentric model.

Varahamihira wrote extensively about eclipses in his work, the Brihat Samhita. He provided detailed descriptions of various types of eclipses, their causes, and their astrological significance.

The ancient Indian observatory at Varanasi was known as Vedhshala. It was a significant center for astronomical studies and observations in ancient India.

Brahmagupta is known for his contributions to trigonometry, including the development of trigonometric identities and formulas. His work, the Brahmasphuta Siddhanta, is a significant treatise on astronomy and mathematics.

Bhaskara II is known for his contributions to calculus, including the development of methods for finding derivatives and integrals. His work, the Siddhānta Shiromani, is a significant treatise on astronomy and mathematics.

Madhava of Sangamagrama is known for his contributions to calculus, including the development of the concept of the derivative and the mean value theorem. His work, the Yuktibhasa, is a significant treatise on astronomy and mathematics.

Nilakantha Somayaji is known for his contributions to trigonometry, including the development of trigonometric identities and formulas. His work, the Tantrasamgraha, is a significant treatise on astronomy and mathematics.