The four largest moons of Jupiter were discovered by Galileo in early 1610 when he first turned his telescope toward the heavens. They are called the Galilean moons in his honor. In a single evening you can observe them move in their orbits around Jupiter; visual proof that Copernicus was correct and our earth is not the center of the universe.
Multiple photographs taken over a three-hour period were combined to create this time-lapse image. The brightness of the moons were adjusted to enhance the illusion of motion; the earliest shots are dimmer. Callisto is the moon furthest left. Europa is on the right. Ganymede is moving left and disappears behind the southern hemisphere of Jupiter, while Io is passing in front of Jupiter and moves off toward the right.
Hold your mouse cursor over the image to see the orbital paths of the moons.
Moons in Motion
26–27 June 2007 at Carlisle, Massachusetts
Questar 3.5″ telescope using positive projection with 16 mm Brandon eyepiece and Nikon D100 at ISO 200
Jupiter is a stack of 35 images, each ½ to 1 sec exposure
The moons are 4 images taken at 1 hour intervals, each 4 sec exposure