The Seeliger Effect

Images taken in the early hours of the morning 28-04-2013 from our backyard

At opposition Saturn's rings brighten. This increase in illumination is known as the 'Seeliger Effect'. A superior planet, ie a planet outside Earth's orbit, is said to be in opposition when it is in a line with the Sun and Earth and nearest to Earth.

The opposition surge (sometimes known as the opposition effect, opposition spike or Seeliger effect) is the brightening of a rough surface, or an object with many particles, when illuminated from directly behind the observer. The term is most widely used in astronomy, where generally it refers to the sudden noticeable increase in the brightness of a celestial body such as a Saturn, as its phase angle of observation approaches zero. It is so named because the reflected light appears significantly brighter than predicted when at astronomical opposition. Two physical mechanisms have been proposed for this observational phenomenon: shadow hiding and coherent backscatter.

Credit to Wikipedia