Obituary: Sergio Cortesi

Sergio Cortesi left us. Doyen of professional and amateur astronomy in Ticino, former director of the Specola Solare Ticinese, with 64 years of activity in the Sunspot observations, among the founders and then long-time president of the SocietĂ  Astronomica Ticinese, Sergio Cortesi is no longer with us. We will miss him very much.