First solar butterfly diagram from Schwabe's observations in 1825–1867

Abstract The original sunspot observations by Samuel Heinrich Schwabe of 1825–1867 were digitized and a first subset of spots was measured. In this initial project, we determined more than 14 000 sunspot positions and areas comprising about 11% of the total amount of spots available from that period. The resulting butterfly diagram has a typical appearance, but with evident north-south asymmetries.