These are the positions of the Galilean moons of Jupiter at UTC
Northern hemisphere view
The positions are calculated using the approximate method described by Jean Meeus in Astronomical Algorithms. This is not accurate enough to predict mutual eclipse of the moons, but good enough to identify them in photographs or when you're looking at them. If you set the date to 7 January 1610 at 1645UT, you'll see their positions just as Galileo drew them (though his telescope was not good enough to separate Io and Europa, a few arcseconds apart, so he drew them as a single object).
The size of Jupiter and the positions of the satellites are on the same scale; the moons themselves are shown as twice their actual size, otherwise they don't show up on small displays. The figure is about 58 Jupiter radii across, corresponding to a field of view of 43 arcmin when Jupiter is near opposition. A camera lens with a focal length of about 2000mm would give you this field of view. Jupiter's colours on this plot were obtained from a Cassini image, averaged in longitude.
animate shows the moon's positions advancing in 20 minute steps, shown at 30,000× the true rate. You can also move forward and back in 5-minute steps using the keyboard arrow keys.