ROYAL ASTRONOMICAL SOCIETY / SCIENCE PHOTO LIBRARY ROYAL ASTRONOMICAL SOCIETY / SCIENCE PHOTO LIBRARY
Phases of Saturn, artwork published in Specula Physico-Mathematico-Historica (1696), a book by the German monk and author Johann Zahn (1641-1707). The artwork has a Latin title (top) and shows the variation in the "phases" of Saturn. This variation (not strictly a phase) is due to the inclination of Saturn and its rings to the ecliptic, varies over a 29-year cycle as Saturn orbits the Sun. The first telescopic observations of Saturn's rings were made by Galileo in 1610, but it was not until better telescopes were used later that century, that the variations seen here were observed.
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