Bruce Murray Space Image LibraryOpposition surge of Saturn’s rings Opposition surge of Saturn’s rings Three views of Saturn captured on different dates with the 2.2-meter telescope at the Calar Alto Observatory in Spain. Phase angles are measured in degrees. On January 13, 2005, Earth crossed the disk of the Sun as seen from Saturn, so Earth-based telescopes saw Saturn and its rings and moons with a "phase angle" (Sun-target-observer angle) of zero degrees. The globe of Saturn does not change much in the three views, but the rings flash into brilliance as the phase angle goes to zero. This effect is called "opposition surge" and was also seen on some of Saturn's moons, especially Enceladus.