Pluto and Charon
Pluto, accompanied by its largest moon Charon, orbits the Sun at a distance usually outside the orbit of Neptune except for a twenty-year period in each orbit.
From Pluto, the Sun is still very bright, giving roughly 150 to 450 times the light of the full Moon from Earth (the variability being due to the eccentricity of Pluto's orbit). Nonetheless, human observers would find a large decrease in available light.
Pluto and Charon are tidally locked to each other. This means that Charon always presents the same face to Pluto, and Pluto also always presents the same face to Charon. Observers on the far side of Charon from Pluto would never see the dwarf planet; observers on the far side of Pluto from Charon would never see the moon. Every 124 years, for several years it is mutual-eclipse season, when Pluto and Charon each eclipse the Sun for the other, at intervals of 3.2 days.
Read more about this topic: Extraterrestrial Skies