Voyager 2 observed Io on the far side of Jupiter in this set of images. This sequence of nine images was collected using the Green filter from about 1.2 million kilometers. A 2.5 hour period is covered during which Io rotates 7 degrees.
Also, during this time, Io moves more directly between the Sun and Jupiter. To an observer on the dark portion of Io, the night would be dominated by the huge bulk of Jupiter in the sky. In this image sequence, as the crescent of Io gets thinner, the appearance of Jupiter from Io becomes more "full" and, thus, brighter. This large bright object in the Io night sky causes the dark "Io-scape" to be significantly illuminated by "Jupiter-shine."