  An analysis of the sunspot observations made by Hevelius during 1642-1645 is
presented. These records are the only systematic sunspot observations just
before the Maunder Minimum. We have studied different phenomena meticulously
recorded by Hevelius after translating the original Latin texts. We re-evaluate
the observations of sunspot groups by Hevelius during this period and obtain an
average value 7% greater than that calculated from his observations given in
the current group database. Furthermore, the average of the active day fraction
obtained in this work from Hevelius' records previous to the Maunder Minimum is
significantly greater than the solar activity level obtained from Hevelius'
sunspot observations made during the Maunder Minimum (70% vs. 30%). We also
present the butterfly diagram obtained from the sunspot positions recorded by
Hevelius for the period 1642-1645. It can be seen that no hemispheric asymmetry
exists during this interval, in contrast with the Maunder Minimum. Hevelius
noted a ~3-month period that appeared to lack sunspots in early 1645 that gave
the first hint of the impending Maunder Minimum. Recent studies claim that the
Maunder Minimum was not a grand minimum period speculating that astronomers of
that time, due to the Aristotelian ideas, did not record all sunspots that they
observed, producing thus an underestimation of the solar activity level.
However, we show the good quality of the sunspot records made by Hevelius
indicates that his reports of sunspots were true to the observations.
