The telescope was invented in the 16th century in Europe, while the astrolabe, gnomon, and sundial were all used in ancient India.

The astrolabe was a versatile instrument that could be used for measuring the altitude of celestial bodies, determining the time of day, and navigating at sea.

The gnomon is a vertical rod or pillar that casts a shadow. The length of the shadow can be used to measure the altitude of the sun.

The sundial is a device that uses the position of the sun to indicate the time of day.

The sundial is the only ancient Indian astronomical instrument that is still used today.

The altitude of a celestial body is the angle between the celestial body and the horizon.

Both the length and direction of the shadow cast by the gnomon are proportional to the time of day.

Both the shadow cast by the gnomon on the sundial and the position of the sun in the sky indicate the time of day.

The ancient Indian astronomers made significant contributions to the field of astronomy, including the development of the decimal system, the discovery of the zero, and the invention of the astrolabe.

The ancient Indian astronomers were able to make accurate observations of the night sky without the use of telescopes because they had a very clear view of the night sky, a deep understanding of the mathematics of astronomy, and a lot of experience observing the night sky.

The ancient Indian astronomers made significant contributions to the field of astronomy, including the development of the decimal system, the discovery of the zero, and the invention of the astrolabe.

The ancient Indian astronomers were able to make accurate observations of the night sky without the use of telescopes because they had a very clear view of the night sky, a deep understanding of the mathematics of astronomy, and a lot of experience observing the night sky.

The ancient Indian astronomers made significant contributions to the field of astronomy, including the development of the decimal system, the discovery of the zero, and the invention of the astrolabe.

The ancient Indian astronomers were able to make accurate observations of the night sky without the use of telescopes because they had a very clear view of the night sky, a deep understanding of the mathematics of astronomy, and a lot of experience observing the night sky.

The ancient Indian astronomers made significant contributions to the field of astronomy, including the development of the decimal system, the discovery of the zero, and the invention of the astrolabe.