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Sunspots Areas and Heliographic Positions on the Drawings Made by Galileo Galilei in 1612

  • Mikhail V. Vokhmyanin (a1) and Nadezhda V. Zolotova (a1)

In 1612, Galileo Galilei made very accurate drawings of the solar disk. Currently, 47 of them are in the open access: 9 in May 3 – 11, 35 in June and July, and 3 in late August. Unfortunately, reports have not provided the clock time, which results in uncertainty of sunspots heliographic coordinates. In the present study, we determine the exact time of the drawings by comparing the positions of the same spots from day to day. The time of the observations, which varies from 12 to 16 UT, gives us the direction of the solar rotation axis and the position of the helioequator. Unlike the spots drawn by Christopher Scheiner in 1611 – 1612, none of the analyzed spots lies within the helioequator. This confirms the quality of the Galileo’s drawings.

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Proceedings of the International Astronomical Union
  • ISSN: 1743-9213
  • EISSN: 1743-9221
  • URL: /core/journals/proceedings-of-the-international-astronomical-union
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