Large telescopes are powerful instruments used to observe distant celestial objects. They collect and focus light, allowing astronomers to study stars, galaxies, and other phenomena in the universe. The size of the telescope's mirror or lens determines how much light it can gather, which is crucial for seeing faint objects. These telescopes can be ground-based, like the Keck Observatory in Hawaii, or space-based, such as the Hubble Space Telescope. Each type has its advantages; ground-based telescopes can be larger, while space telescopes avoid atmospheric interference, providing clearer images of the cosmos.