HSUNSPOTS: A tool for the analysis of historical sunspot drawings

Valuable information about the evolution of solar activity is recorded in early sunspot drawings, especially during 17th–19th centuries. In this context, we have developed a computer program to analyze historical drawings showing the trajectories of sunspots across the solar disk. As an example, we have analysed the drawings published in the book De heliometri structura et usu by Zucconi (1760). These drawings span the period from April 1754 to June 1760. We present the Butterfly diagram for those years. The ending of solar cycle 0 and the beginning of solar cycle 1 are clearly noted in this diagram.