The astronomical device used to observe celestial bodies is called a telescope. Telescopes come in various types, including refracting telescopes that use lenses and reflecting telescopes that use mirrors. They have revolutionized our understanding of the universe by allowing astronomers to observe distant stars, planets, and galaxies with increased clarity. Telescopes have contributed to numerous significant discoveries, such as the moons of Jupiter and the rings of Saturn. Modern telescopes, including space-based observatories like the Hubble Space Telescope, provide unparalleled views of the cosmos, leading to advancements in our comprehension of the universe's structure and dynamics.