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Nature volume 127, page 462 (21 March 1931) | Download Citation



The Corona without an Eclipse.—M. B. Lyot's experiments with a sensitive polarimeter from the summit of the Pic du Midi, which is 9439 feet high, undoubtedly indicate the most hopeful means of observing the corona without an eclipse. They are fully described in a bulletin dated Feb. 14 issued by Science Service, Washington, D.C. A screen was used to cover the image of the sun's disc, and the prominences were then visible without the aid of a spectroscope. The polarised light that he ascribes to the corona can only be traced for 3′ or 4′ above the sun's limb, so that the method only extends to the bright inner zone of the corona. It is only observed in one position angle at a time; but by rotating the instrument round the sun's limb, it can be studied in all position angles. Dr. Deslandres is hopeful that it may be possible to photograph the images thus obtained. The article recalls that Francois de Plantade, an assistant of Cassini, used the Pic du Midi for astronomical observations two centuries ago. It also refers to the attempts of Prof. Hale and Dr. Steavenson to photograph the corona from high mountains; they did not, however, employ a polarimeter. A complete check of the new method will be afforded when the moon is very near the sun, but not actually encroaching on the disc; if the method is sound, the dark disc of the moon should be discernible.

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