Galileo and Sunspots

The use of the telescope to observe sunspots began about 1610. Although large sunspots were noticed before the invention of the telescope and could be seen with the naked eye at sunset or through a filter the invention of the telescope encouraged research. Galileo may have responded to criticism about the possibility of injury to the eye and turned to a novel method to observe sunspots as this video shows. The 400 year anniversary of Galileo's first letter on sunspots will be a few days from now on May 4, 2012. This letter has drawings of sunspots in it (see p. 22). The phrase "macchie solari" is Italian for sunspots.