There were no telescopes prior to 1608, so no "ancient" astronomers ever used one.
Galileo Galilei was the first astronomer to make extensive use of the telescope for astronomy. He made several important discoveries, such as the moons of Jupiter and the phases of Venus, using his telescope in the early 17th century.
Galileo Gailei is the first person credited with using the telescope for astronomical observations. He did not invent the telescope. He is the first to have seen moons going around Jupiter, the rings of Saturn (though he incorrectly identified them), and that the Moon had cliffs and craters.
While not the inventor of the telescope, Galileo is widely believed to be the first person to use a telescope for astronomy.
after he made it
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A telescope.
Galileo was the first person to use a telescope for astronomical research.
The first person to use a telescope for astronomical observation was Galileo Galilei in the early 17th century. He made groundbreaking discoveries, such as the moons of Jupiter and the phases of Venus, using his telescope.
It didn't - the planet Saturn was observed in ancient times, but Galileo was the first to view it through a telescope and discover its rings in 1610.
Galileo
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