A coronagraph is a specialized instrument used in astronomy to block out the bright light of a star in order to observe faint objects nearby, such as planets or other celestial bodies. By effectively reducing the brightness of the star, a coronagraph allows astronomers to detect and study objects that would otherwise be obscured. Coronagraphs are used in both ground-based telescopes and space telescopes to improve the contrast and resolution of astronomical observations. This technology has been crucial in the study of exoplanets and their atmospheres, as well as other faint and distant astronomical phenomena.