Modern View of the Sun: Materials for an Experimental History Before the Telescope

Galileo and the telescope revolutioned the concept of the Sun. The discovery of its rotation was possible with the continuous observation of the sunspots. The faculae and the maculae with umbra and penumbra become daily accessible to the new instruments, leaving the perfectly lucid disk only to the realm of symbolisms. Was this new view possible before the telescope? Technically the pinhole-cameras can show the largest sunspots, as well as the naked eyes under very particular conditions, but the observations were too scattered to produce any change in the Sun’s established concept. Synoptic observations of the largest sunspots of the cycle XXV made with naked eye, pinholes-camera and a telescope in camera obscura are presented and compared with the historical ones. The sunspots could have been discovered in Florence since 1475 with the pinhole-meridian line of S. Maria del Fiore: the Spörer minimum (1460-1550) of solar activity prevented it.