Jupiter

Jupiter is the largest planet in the solar system - 11 times Earth’s diameter - and even though it’s five times farther from the Sun than Earth is, its sheer size makes it appear big in telescopes. At opposition, Jupiter spans about 45-50 arcseconds, nearly as large as Mars at its absolute closest approach. But unlike Mars, Jupiter reaches opposition every 13 months, so you get frequent opportunities to observe it well.

Even a small 60mm telescope shows Jupiter as a disk with visible cloud bands and its four largest moons - the Galilean moons - lined up on either side like tiny stars. With a 100mm telescope or larger, Jupiter becomes a world of detail: multiple cloud bands, the Great Red Spot (when it’s visible), storms, festoons, and the constantly shifting positions of the moons.

What You Can See

Cloud bands are the most obvious feature. Jupiter’s atmosphere is divided into alternating light zones and dark belts running parallel to the equator. The two most prominent are the North Equatorial Belt (NEB) and South Equatorial Belt (SEB), which are visible even in small scopes at moderate magnification. With larger apertures and good seeing, the bands show structure: waves, swirls, turbulence along the edges where zones and belts meet. Jupiter’s atmosphere is violent and dynamic, and you can see that chaos when conditions allow.

The Great Red Spot (GRS) is a massive storm larger than Earth that’s been raging for at least 300 years. It’s not as prominent as it used to be - it’s faded over the past few decades - but it’s still visible as an oval reddish-orange feature in the southern hemisphere. It rotates into view roughly every 10 hours as Jupiter spins. Apps and websites publish transit times showing when the GRS crosses Jupiter’s central meridian - the best time to observe it.

The Galilean moons - Io, Europa, Ganymede, and Callisto - are visible in any telescope and most binoculars. They change positions noticeably over just a few hours. One night you might see all four on one side. The next night, they’re scattered. Sometimes one or more disappear behind Jupiter or pass in front of it, casting a tiny shadow on the cloud tops (visible in telescopes 150mm and larger with good seeing). Watching the moons move in real time over a single night is mesmerizing. You’re seeing orbital mechanics play out in front of you.

When and How to Observe

Jupiter is visible for about 10 months out of every year, disappearing behind the Sun for only a couple of months during conjunction. Opposition is the best time - Jupiter is closest, brightest, and highest in the sky at midnight - but honestly, Jupiter looks good for several months before and after opposition.

Start at moderate magnification (50-100x) to get an overview. Then increase magnification to 150x, 200x, or even higher if seeing allows. Jupiter is bright enough to handle high power, and detail improves with magnification as long as the atmosphere stays steady.

Jupiter rotates in just under 10 hours. If you observe for an hour or two, you’ll see features drift across the disk. Clouds near the equator move faster than those at higher latitudes, creating the sheared, turbulent look Jupiter is known for.

Use apps to track the Great Red Spot’s position. If it’s on the far side of Jupiter when you start observing, wait an hour or two and it’ll rotate into view.

The Bottom Line

Jupiter never disappoints. It’s big, detailed, dynamic, and accessible. Small telescopes show real features. Large telescopes reveal an atmosphere in constant motion. And the Galilean moons provide a show every single night. If you’re new to planetary observing, start with Jupiter. It’s forgiving, impressive, and endlessly interesting. Even experienced observers return to Jupiter again and again because there’s always something new - a storm developing, a moon transiting, the GRS drifting into view. Jupiter is the planet that keeps people coming back.