If you point your telescope at Jupiter during a clear hour or two after nightfall, you will see possibly as many as 4 satellites (moons) adjacent to Jupiter. These moons are named Io, Europa, Ganymede and Callisto. Every night you will get a different ‘snapshot’ view of the moons. Your view of Jupiter and the moons is superior to the one Galileo had through his small refractor telescope. However his was the thrill of a lifetime:
“Try to imagine what must have gone through Galileo Galilei’s mind one January evening in 1610 when he first realized that the four points of light he saw through his new telescope were, in fact, worlds circling Jupiter. The thrill of discovery would have been magnified by the simultaneous realization that an unshakable truth — that all worlds revolved around the Earth — had just collapsed. Although viewing these same moons might not shake up your own world view, you can at least relive some of Galileo’s excitement by discovering them for yourself with nothing more than binoculars or a small telescope”
—courtesy Sky and Telescope: http://www.skyandtelescope.com/observing/objects/planets/3307071.html
Now, once you have captured the nightly parade, to find out which moon is which, use the free software program stellarium to identify the moon dancers.
- Set the approximate time and date of your observation 2. Find and Zoom in on Jupiter until you see the moons
On April 24, 2017 for example, 21:00 EDT We saw this ‘hockey stick’ configuration of the 4 moons. On some nights you may just be lucky enough to see the moons disappear behind the planet from our line of sight or even to produce shadows on Jupiter – these are called “shadow transits” . For this you need a large scope, with high enough magnification to see it.