Abstract
Jean Tarde and Jan Smogulecki carried out sunspot observations in the 1610s and 1620s at the dawn of the telescopic era. We analysed their original observational records to revise their sunspot-group numbers in the existing database. In this study, we provide a new counting as a basis for future scientific discussions. Furthermore, we compared Smogulecki’s sunspot observations with those of Scheiner and Schönberger on the same observation days. We also detected a big sunspot group on 2 – 3 February 1622 in Smogulecki’s sunspot drawings and estimated its area to be approximately 1600 millionths of the solar disc. In addition, we measured the sunspot positions in Tarde’s and Smogulecki’s sunspot drawings to construct a butterfly diagram for this early period.
Highlights
Sunspots have been observed for several millennia, they started to be more systematically recorded since 1610, after the use of the telescope as an astronomical instrument (Yau and Stephenson, 1988; Vaquero and Vázquez, 2009; Hayakawa et al, 2017; Willis et al, 2018)
We found five days of Smogulecki’s sunspot observations (2 and 3 November 1621 and 2, 3, and 12 February 1622) that were overlooked in V16, whereas we found nothing for this work are represented by green (Tarde)’s sunspot observations
We have revised the sunspot observations made by Tarde in 1615 – 1617 and Smogulecki in 1621 – 1625
Summary
Sunspots have been observed for several millennia, they started to be more systematically recorded since 1610, after the use of the telescope as an astronomical instrument (Yau and Stephenson, 1988; Vaquero and Vázquez, 2009; Hayakawa et al, 2017; Willis et al, 2018). 170 Page 2 of 14 disc were used to calculate the indices of the relative sunspot number and group sunspot number (Hoyt and Schatten, 1998; Clette and Lefèvre, 2016). These indices, derived from their counting, have been extensively used to characterise long-term solar activity, as they have been constructed from direct solar observations for the last four centuries. Recent studies have detected some problems with these sunspot-number indices (Clette et al, 2014) This was the case with their background database (Hoyt and Schatten, 1998), which has been significantly revised and updated based on the original records (Vaquero et al, 2016).
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