U.Mars — Encyclopedia
The Solar System
To observe Jupiter we can make note of — after the manner of Galileo — the positions of the moons over the course of a few nights, taking observations hour to hour. Since we are viewing the orbits edge-on, we see the moons going from side to side rather than in circles.
Some of the moons go around more quickly than others, which is why we need to look both over the course of a single night and over the course of a few nights.
