Early Astronomy in the University of Michigan Collections

De Maculis: Engraving

In this engraving, AB represents the Sun, from whose center, C, an arc is drawn, DE, which shows the path of some spot around the Sun. For instance, let us imagine that the spot is at D, that is, between the Sun, AB, and the eye, F, which is positioned on Earth. The only rays that could descend from the Sun through the spot are AF and GF. Therefore, the rays transmitted through the spot are much weaker, making the spot in this location appear barely illuminated to the eye, therefore, very dark. Put differently, the structure of this diagram helps explain Scheiner’s theory of the sunspots being the shadows of stars (satellites) orbiting around the Sun.

On Sunspots



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