Analyses of Early Sunspot Records by Jean Tarde (1615 – 1617) and Jan Smogulecki (1621 – 1625)

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.