Abstract
MANY years ago it was predicted that stars close to the sun should be visible to an observer using a suitable technique. Only recently, however, has such a technique been developed, primarily for investigating the solar corona without waiting for a total eclipse. News has now reached Great Britain that a Swiss attempt to photograph stars in daylight with the aid of a coronagraph has been successful (M. Waldmeier, Z. Astrophys., 21, 269 ; 1942). A photograph obtained at Arcsa, at an altitude of 2,050 in. in the Alps, shows Rcgulus (mag. 1 -34) quite clearly at a distance of 12' (less than the sun's angular radius) from the edge of the solar disk. The observation is possible only by eliminating so far as possible diffracted and diffused light in the apparatus, and by observing at a great altitude to avoid meteorological scattering. The successful photograph was obtained at midday on August 22, 1941, with a 15-sec. exposure through a red filter. Begulus is the only first-maguitude star within 1° of the ecliptic, but there are a number of fainter stars (down to third magnitude) which, it is considered, could be photographed in favourable conditions.
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Photography of Stars in Daylight. Nature 152, 158 (1943). https://doi.org/10.1038/152158a0
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DOI: https://doi.org/10.1038/152158a0