The giant planet is a telescope-user’s delight with interesting cloud belts, spots, and other fascinating features.
A 100mm (4-inch) or larger telescope can provide fantastic views of Jupiter. Start your session off by identifying both the north and south equatorial bands. Good seeing may allow for the temperate bands at each pole to be seen. The Great Red Spot, a storm the size of the Earth, can be seen if it is positioned facing the Earth. A list of times that the G.R.S. can be observed can be found here. With experience, you may be able to discern festoons, barges and ovals on the surface of Jupiter.
Shadow transits, eclipses of the Sun upon the surface of Jupiter by Io, Europa, Ganymede and Callisto, the four largest moons of Jupiter, can also occasionally be seen.
Some coloured filters may enhance planetary details. Light blue (80A), very light blue (82A) and light green (56) often accentuate surface features of Jupiter. Remember that detail will not magically appear with the use of a coloured filter and that using one which is too dark for your telescope can reduce the amount of visible detail. If the Great Red Spot cannot be seen without a filter, it will not prominently pop into view once a filter is used.
Owners of achromatic refractor telescopes may benefit from the use of a minus-violet filter. These filters attach to the bottom of an eyepiece or to the telescope’s diagonal, reducing the amount of chromatic abberation while increasing contrast and detail.
Remember to be patient while observing the planets. Brief glimpses of subtle detail may pop into view for only a fraction of a second, but that moment may provide you with a wealth of visible detail. Seeing detail on the planets requires that you spend time at the eyepiece. Your eye will become trained to see more detail after a few observing sessions, and remember that the more you look, the more you’ll see.