In all human cultures the Sun played a major role and was thus observed by astronomers. Sunspots were observed already more than 2000 years ago by Chinese and Greek scientists. In the 19th century it became clear that the number of sunspots was related to the solar activity and undergoing a cyclic change. Since then sunspots are counted systematically by various observatories around the globe and define cycle of solar activity.

With the CESAR solar telescope, taking pictures every week, we can participate in the world wide campaign of sunspot counting.