Abstract
Observations of a sunspot during and after a partial solar eclipse are described. The amount of scattered light confirms the existence of a spread function component with a half width of 10″. The observations also indicate the possibility of severely underestimating this component by aureole measurements. Umbral continuum intensities of 0.10 I ⊙ in the red spectral region were directly measured, the correction for scattered light amounts to 0.02 I ⊙. Intensities calculated with four umbral models are larger than the observed values, indicating this sunspot to be cooler by some 100 K. The wings of two strong Ca i lines are equally explained by the models of Henoux, Kneer, and Stellmacher/Wiehr. Yun's model can be ruled out because of too high a temperature.
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Mitteilungen aus dem Fraunhofer Institut, Nr. 134.
Leaving for Institut für Theoretische Astrophysik, D-69 Heidelberg, Im Neuenheimer Feld 294, F.R.G.
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Köppen, J. Sunspot and stray light observations during the 1971, February 25 partial solar eclipse. Sol Phys 42, 325–332 (1975). https://doi.org/10.1007/BF00149915
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DOI: https://doi.org/10.1007/BF00149915