(redirected from coronograph)
Also found in: Dictionary, Wikipedia.
Related to coronograph: spectroheliograph


coronagraph (kərōˈnəgrăfˌ), device invented by the French astronomer B. Lyot (1931) for the purpose of observing the corona of the sun and solar prominences occurring in the chromosphere. Because of the intense light of the sun, the corona and chromosphere can ordinarily be seen only during a total eclipse. The coronagraph consists of two refracting telescopes in tandem. A solid disk placed in front of the prime focus of the first telescope plays the part of the moon and eclipses the sun's image in the telescope so that only the outer layers of the sun's atmosphere are focused by the second telescope onto photographic film. A monochromatic filter is also used to improve optical clarity and remove chromatic aberration.
The Columbia Electronic Encyclopedia™ Copyright © 2022, Columbia University Press. Licensed from Columbia University Press. All rights reserved.


(kŏ-roh -nă-graf, -grahf) An optical instrument designed in 1930 by the French astronomer Bernard Lyot for observing the solar corona at times other than a total solar eclipse. In the coronagraph, the bright image of the Sun is artificially eclipsed by means of a blackened occulting disk set at the prime focus of the objective lens of a refracting telescope. A lens is used because the scattering of light from its surface is much less than is the case with a mirror. It is important to reduce scattering to a minimum if the faint light of the corona is to be recorded on the photographic plate or other detector. To reduce atmospheric scattering, high-altitude sites are used; coronagraphs have also been operated from satellites, rockets, and balloon platforms. A narrow-band interference filter is usually placed in front of the detector so that the emission lines of the E-corona can be studied.
Collins Dictionary of Astronomy © Market House Books Ltd, 2006
The following article is from The Great Soviet Encyclopedia (1979). It might be outdated or ideologically biased.



a telescope used for observation of the corona of the sun. Since the light scattered from the sun’s photosphere in the earth’s atmosphere and in the telescope is hundreds of times brighter than the light of the sun’s corona, the latter was observed until the 1930’s only during total solar eclipses, when the photosphere is covered by the moon. The coronagraph used for such observations is a long-focus photo-graphic camera, usually mounted horizontally; the light to it is supplied by a coelostat. The standard coronagraph used in the USSR has an objective of 5-cm diameter and 500-cm focal length.

Observations of the corona of the uneclipsed sun became possible after the invention of a coronagraph by the French astronomer B. Lyot, by means of which he first observed the corona at the observatory at Pic-du-Midi (France) in 1931. The corona-graph used to observe the uneclipsed sun consists of a primary objective that forms an image of the sun on a metallic disk, which occults the light of the photosphere and thus produces an artificial eclipse. In order to eliminate the scattered light that appears around the edge of the primary objective as a result of diffraction, a lens is placed behind the metallic screen. This lens forms the image of the primary objective on a diaphragm, which has an opening too small to pass the image of the edges of the primary objective. A second objective forms the final image of the corona or prominences on a spectrograph slit or on a photographic plate. In the last case, the light passes through a monochromatic interference-polarization filter, which removes all rays except the spectral line of the corona or prominence being studied. The use during observations of special filters with a density that decreases from the center to the edges makes it possible to obtain images of the bright inner part and of the fainter outer part of the corona on the same photograph.

Coronagraphs provide best results when set up on mountains, where the atmospherically scattered light is significantly less. In the USSR the first observations of the corona of the uneclipsed sun were made at the Kislovodsk Mountain Astronomical Station in 1950, using a coronagraph with an objective of 20-cm diameter. The largest coronagraphs in the world, with objectives of 53-cm diameter, are located at this station and at the observatories near Irkutsk, in Abastumani, and in Alma-Ata.


Gnevyshev, M. N. Kislovodskaia gornaia astronomicheskaia stantsiia. Moscow-Leningrad, 1965.
Martynov, D. la. Kurs prakticheskoi astrofiziki, 2nd ed. Moscow, 1967.


The Great Soviet Encyclopedia, 3rd Edition (1970-1979). © 2010 The Gale Group, Inc. All rights reserved.


An instrument for photographing the corona and prominences of the sun at times other than at solar eclipse.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.
References in periodicals archive ?
Once the twinkle was removed, the light from the star itself was blocked using the team's coronograph, an instrument that selectively masks out the star.
Other sections cover solar telescopes, wavefront sensing and control, mirror technology, NASA's Terrestrial Planet Finder missions, and coronographs. There is a wealth of material on future missions, with papers on the extrasolar planetary imaging coronograph, completing the census of extrasolar planets in the Milky Way with the microlensing planet finder, the science case and mission concept for the Single Aperture Far-Infrared (SAFIR) observatory, the identification of organic molecules in space, and expected effects of hot CCD pixels on detection of transits of extra-solar planets with the Kepler mission.
"This event is not observable, of course, except with a coronograph. I urge any observatory with such an instrument to take pictures of Venus approaching the Sun's limb.
Since then, ground-based coronographs have been used to separate out the faint coronal light from the bright sky and the Sun's powerful rays, but at the cost of detail in their images and precision in their measurements.
The corona of the active Sun is filled with structures easily observed using white-light coronographs [154,155].
Many comets were discovered with the SOHO LASCO coronographs and were not observed elsewhere.