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Sunspot positions from various historical sets of solar drawings are analysedwith respect to the tilt angles of bipolar sunspot groups. Data by Scheiner,Hevelius, Staudacher, Zucconi, Schwabe, and Spoerer deliver a series of averagetilt angles spanning a period of 270 years, additional to previously foundvalues for 20th-century data obtained by other authors. We find that theaverage tilt angles before the Maunder minimum were not significantly differentfrom the modern values. However, the average tilt angles of a period 50 yearsafter the Maunder minimum, namely for cycles 0 and 1, were much lower and nearzero. The normal tilt angles before the Maunder minimum suggest that it was notabnormally low tilt angles which drove the solar cycle into a grand minimum.

Sunspot group tilt angle measurements from historical observations