Observations of stray-light and sunspot intensities during the Mercury transit of 1970 May 9

✍ Scribed by W. Mattig

• Book ID: 104642633
• Publisher: Springer
• Year: 1971
• Tongue: English
• Weight: 428 KB
• Volume: 18
• Category: Article
• ISSN: 0038-0938
• DOI: 10.1007/bf00149065

✦ Synopsis

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 10 and aureole intensities < 0.01 Io. The stray light correction to the spot intensities has been < (0.03 i 0.01) lo. The main contribution to the stray light on the solar disc is shown to be produced by a spreadfunction with a half width of 10 arc sec. Consequently, for stray light corrections the range R <<. RO + + 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.