期刊
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
卷 488, 期 3, 页码 3804-3809出版社
OXFORD UNIV PRESS
DOI: 10.1093/mnras/stz1936
关键词
Sun: photosphere; sunspots; Sun: activity
资金
- Ministry of Innovative Development of the Republic of Uzbekistan
- NASA [NNX15AE95G]
- International Space Science Institute (ISSI), Bern, Switzerland
- Russian Foundation for Basic Research [RFBR 19-02-00088]
- Ministry of Education and Science of the Russian Federation [KPi19-270]
- NASA [NNX15AE95G, 805288] Funding Source: Federal RePORTER
Early telescopic observations of sunspots were conducted with instruments of relatively small aperture. These instruments also suffered from a higher level of scattered light, and the human eye served as a 'detector'. The eye's ability to resolve small details depends on image contrast, and on average intensity variations smaller than approximate to 3 per cent contrast relative to background are not detected even if they are resolved by the telescope. Here we study the effect of these three parameters (telescope aperture, scattered light and detection threshold of human vision) on sunspot number, group number and area of sunspots. As an 'ideal' dataset, we employ white-light (pseudo-continuum) observations from the Helioseistnic and Magnetic Imager (HMI) on board the Solar Dynamics Observatory, and we model the appearance of sunspots by degrading the HMI images to corresponding telescope apertures with added scattered light. We discuss the effects of different parameters on sunspot counts and derive functional dependences, which could be used to normalize historical observations of sunspot counts to a common denominator.
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