Observations of stray-light and sunspot intensities during the Mercury transit of 1970 May 9 |
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Authors: | W. Mattig |
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Affiliation: | (1) Fraunhofer Institut, Freiburg i. Br., Germany |
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Abstract: | In order to test the usual method for correcting sunspot intensity measurements for stray light, we have measured, during the Mercury transit of 1970 May 9, the intensities of Mercury, a sunspot umbra, and the aureole. The direct observations result in Mercury intensities < 0.06 I and aureole intensities <0.01 I. The stray light correction to the spot intensities has been <(0.03 ± 0.01) I. The main contribution to the stray light on the solar disc is shown to be produced by a spread-function with a half width of 10 arc sec. Consequently, for stray light corrections the range R R + + 20 in the aureole has to be measured very precisely; furthermore, a remarkable fraction of the stray light in the center of an umbra originates from the surrounding penumbra.Mitteilungen aus dem Fraunhofer Institut, Nr. 102. |
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