From Bad Astronomy
On April 9, 2007, Hubble filmed Jupiter and it’s largest moon Ganymede as the moon passed behind the planet and released the video of it yesterday. Here is Phil Plait’s Flickr version of it, which he posted on his blog:
In case you’re wondering, yes, it is sped up. The sequence was filmed over two hours and the video is only 18 seconds (540 frames at 30 frames/second), so it’s sped up by a factor of 400, if you want to get some sense of the actual time scale. Anyway, the actual Hubble site linked above has some higher resolution versions of this for those so inclined.