displacement: Janus passing Epimetheus, photographed by Cassini, 1st February 2010.
Each successive frame is superimposed, displaced to the right. Epimetheus is held in centre frame (forming a horizontal line) as Janus moves behind it (diagonal line).
The arcs (left, right, and faintly above) are more of a mystery. I wondered if they might be background stars, apparently moving due to the motion of Cassini with respect to Epimetheus. But, on consideration, I think distant stars would exhibit far less apparent motion than that.
Image credit: NASA/JPL/SSI. Animation: AgeOfDestruction.
