Abstract
IF it is true, as Mr. Buss suggests, that variations in the intensity of the components of the emission line K2 on either side of the absorption line K3 are sufficient to account for the dark markings occasionally found in spectroheliograms, then the Kodaiknal plates should show them as conspicuously as those taken with a high dispersion instrument, which isolates the central line. Yet this, as Mr. Buss has himself pointed out, is not the case. In studying high dispersion spectrum photographs of the solar disc, one occasionally discovers places where the K3 line is abnormally dark, and the same thing may also be well observed in the line Hα. When the spectroscope slit chances to cross one of these linear markings, an intensely black spot is seen on the absorption line, and this will usually remain visible or run along the line if the solar image is moved slightly. In the case of the lines H and K, the components of the emission lines H2 and K2 are, I think, always weak at the points of greatest darkness in the absorption lines, and for this reason they may possibly contribute somewhat to the final result in our plates.
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EVERSHED, J. Absorption Markings in “K” Spectroheliograms. Nature 87, 111 (1911). https://doi.org/10.1038/087111a0
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DOI: https://doi.org/10.1038/087111a0
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