Aryabhata, who lived in the 5th century CE, made significant contributions to astronomy, mathematics, and trigonometry. He propounded the heliocentric theory, which placed the Sun at the center of the solar system.

The Rigveda, one of the four Vedas, contains hymns and verses that touch upon various aspects of astronomy and cosmology. It mentions celestial bodies, constellations, and astronomical phenomena.

Aryabhata, in his treatise 'Aryabhatiya,' put forth the concept of a spherical Earth rotating on its axis. This idea was revolutionary for its time and challenged the prevailing flat-Earth belief.

The astrolabe was an important instrument used by Indian astronomers to measure the altitude of celestial bodies above the horizon. It allowed them to determine the time, latitude, and longitude.

Aryabhata, in his work 'Aryabhatiya,' presented a method for calculating the circumference of the Earth using trigonometry. His estimate was remarkably accurate for its time.

The ancient Indian astronomers divided the zodiac into 12 equal parts, known as rashis or signs. Each sign is associated with a constellation and has its own unique characteristics and symbolism.

Aryabhata, in his work 'Aryabhatiya,' suggested that the Moon's surface is not smooth but has mountains and valleys. This idea was later confirmed by telescopic observations.

The ancient Indian astronomers developed the Hindu calendar, also known as the Panchang, which is based on the lunar and solar cycles. It is widely used in India and other parts of South Asia.

Aryabhata, in his work 'Aryabhatiya,' presented a method for calculating the time of eclipses, both solar and lunar. His method was based on his understanding of the motion of the Sun, Moon, and Earth.

The ancient Indian astronomers used the constellation Aries to mark the beginning of the new year. This is because the Sun enters the sign of Aries during the spring equinox, which is considered an auspicious time for new beginnings.

Bhaskara II, in his work 'Siddhanta Shiromani,' proposed a theory of planetary motion that incorporated elliptical orbits. This theory was a significant advancement in astronomy and provided a more accurate description of planetary motion.

The quadrant was an instrument used by ancient Indian astronomers to measure the altitude of celestial bodies above the horizon. It consisted of a quarter-circle arc with markings for measuring angles.

Aryabhata, in his work 'Aryabhatiya,' presented a method for calculating the distance between the Earth and the Moon. His method was based on the observation of lunar eclipses.

The ancient Indian astronomers used the constellation Cancer to mark the beginning of the monsoon season. This is because the Sun enters the sign of Cancer during the summer solstice, which is associated with the onset of the monsoon rains in India.

Brahmagupta, in his work 'Brahmasphuta Siddhanta,' developed a theory of planetary motion that incorporated the concept of epicycles. Epicycles are small circles that are used to explain the variations in the motion of planets.