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An instrument for observing the Sun's corona, which is normally seen only at a total solar eclipse. Invented by Bernard Lyot in 1930, the coronagraph is a special telescope in which an occulting disc at the prime focus creates an artificial eclipse. This device allows the faint light of the corona, which is normally overwhelmed by light from the disc of the Sun, to be isolated. However, even with a coronagraph located at a site where the sky is very clear, scattering of light by the Earth's atmosphere is a problem. This is partly overcome by the use of special filters or by observing the coronal light with a spectrograph.
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