A coronagraph is a feature or attachment for a telescope designed to block light from a bright object in view so that other objects can be seen more clearly. The term was originally used for devices to assist in viewing the Sun's corona, but the term is now used for similar devices blocking star light, for example, for direct imaging of extra-solar planets. Coronagraphy is astronomy, e.g., observation, making use of coronagraphs. The phrase inner working angle refers to the smallest angle between the planet and the star, as seen from the telescope, at which the planet can be detected.
The terms occulter and coronagraph are sometimes used like synonyms and other times, the part of the coronagraph actually blocking the light is called the occulter. The word occulter also is used for starshades, occulting bars and for the bodies that occult in occultations.