Jupiter reaches opposition on February 6, 2015. Find out how to see the planet king at its best.
If you've ventured out at night this winter season, you may have noticed the dazzle of Jupiter among the stars of Leo and Cancer. This is undoubtedly the best time of the year to view the king of the planets. It reaches opposition on February 6th, which means that — assuming clear weather and dark skies — it's easily spotted with the naked eye from dusk to dawn. Appearing low in the east at twilight, Jupiter rises through the southeast sky to shine high in the south around midnight. It's bright this month, too, opening February at this year's peak magnitude of –2.6 and dimming only to –2.5 by month's end. It's not surprising that Jupiter's a favorite target for naked-eye observing. It's up all night, it's bright, and its distinctive yellow-orange color makes it easy to identify.
Jupiter is also a favorite target for observers with binoculars and telescopes, partly because of the variability of its features. As S&T Senior Editor Alan McRobert noted recently, "There's always something happening on Jupiter," and even a modest telescope can be used to see the subtly shifting "stripes" that comprise the planet's zones and belts. Move up to a 6-inch scope and add an appropriate filter, and the horizontal bands become even more readily apparent.To highlight the Great Red Spot and the burnt-umber equatorial belts, experiment with blue (Kodak Wratten number) 38A; medium blue 80A; or light blue 82A filters. Try a yellow 8 or 12, or even a yellow-green 11, to darken the blue festoons (the thin, dark streamers that cut from belt to zone) or to increase the contrast in the polar regions. If you're having trouble detecting the festoons, consider a red 21, 23, or 25. I've found that a red filter really increases the visibility of the blue regions. It should also sharpen the definition between the zones and belts.
But don't let me determine your filter choice. Although generally it's good advice to use a filter opposite in color to the feature you're trying to highlight, Jupiter is a quickly-changing target and observing preferences aren't universal. Filters may help, but they're not required! Visit John McAnally's observing guide for more tips on observing Jupiter.
The mutable nature of Jupiter's features make the planet an observing challenge: although easily located in the sky, you could spend the rest of your life swapping out filters and eyepieces to study zones, belts, rifts, and storms.
Truthfully, telescopes aren't even required for the most fun you'll have with this planet. A set of hobby binoculars will reveal some of Jupiter's best features: its moons. In my 8 x 42 binoculars, Jupiter is a gleaming white disk, noticeably broader than a star. Flanking the disk, in a slightly ragged formation, are three (or four, on a good night) star-like points. These gleams are Io, Europa, Ganymede, and Callisto, the Galilean moons, named so after Galileo Galilei, who first spotted them through a telescope. Galileo noted the location of the moons each night for several months and included a chart of their locations in his 1610 book, Sidereus Nuncius (Sidereal Messenger).