ROYAL ASTRONOMICAL SOCIETY / SCIENCE PHOTO LIBRARY ROYAL ASTRONOMICAL SOCIETY / SCIENCE PHOTO LIBRARY
Sun projection. Diagrams showing various ways to use the reflection of the sun to study its surface patterns and sunspots during the early 1600s. German astronomer Christoph Scheiner (1575-1650) can be seen mapping sunspots with the help of an assistant at bottom. Sunspots are dark areas on the Sun's surface caused by fluctuating magnetic fields within the Sun. Scheiner was the co-discoverer of sunspots and published his great work, the 'Rosa Ursina', in the 1630s, from which this illustration was taken. It was the standard treatise on the subject for more than a century, containing numerous observations and also a detailed account of his methods and apparatus.
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