The instrument primarily used to look at the stars is the telescope. Telescopes are optical devices that collect and magnify light from celestial objects, allowing astronomers to observe distant astrophysical phenomena. There are various types of telescopes, including refractors, which use lenses, and reflectors, which use mirrors. The invention of the telescope revolutionized astronomy, enabling discoveries such as the moons of Jupiter and the rings of Saturn. Telescopes can be ground-based or space-based, with space telescopes, like the Hubble, providing clearer views free from Earth's atmosphere, thereby expanding our understanding of the universe.