The Jupiter View Through A Large Telescope

The Public Domain Jupiter Image was Supplied by NASA/NSSDC This Site Not Endorsed by NASA

The Jupiter image above is typical of what an amateur astronomer might see on a good evening with a 10 inch or so telescope. Actually, the colors here are more vivid than what might actually seen through a telescope. But the details and Jovian features are about what a large telescope can observe.

The Jupiter View Through A Smaller Telescope

At left is an impression of Jupiter that a smaller telescope might give. First you'll notice that the image appears in mostly shades of gray, and the finer details are lost. The image also has much less contrast. Still an enticing image, but not like you see in text books and magazines. Check out the Simulated Views page for examples of what Jupiter details are visible through different sized telescopes.

However, even with a small telescope, such as the commonly used 60mm refractor, you can still make out the major cloud bands of Jupiter. You can also see the 4 Galilean moons of Jupiter. In fact, the big moons of Jupiter are even visible as pin points of light through nothing more than a pair of binoculars.

It's very helpful to plan a bit when going out to view Jupiter. By that I mean it's nice to know what you are likely to see. You may want to find out what nights of the week something interesting is happening that would be fun to view. There are a number of ways to do that planning. One of the best ways to plan a Jupiter observing evening is with a computer planetarium program, such as xephem, kstars, or stellarium.

You can also use this website to see what tonight's Jupiter view will be.

The depiction at left is the Jupiter View from the planetarium program Xephem. It shows the appearance of Jupiter and it's moon for tonight at about 8:00 PM Denver time. If you check this image each day, you'll have some idea of when something interesting is about to happen. More of tonight's sky presentations are available at Tonight's Sky. The moons in this image are labeled with Roman numerals, with I = Io, II = Europa, III = Ganymede, and IV = Callisto. To see whether the Great Red Spot on Jupiter is visible at any given time, you can check out the Sky and Telescope Jupiter Applet.

The Xephem diagram above will show you when the Great Red Spot is visible, and when Jupiters moons are in interesting configurations, or when one or more are casting shadows as they move across the planet.

Some Jupiter Nomenclature

Observers of Jupiter use a set of abbreviations to indicate the features of Jupiter. Being familiar with them will help you understand more of what you read about Jupiter.

At left is a drawing with the zones and belts labeled with their common nomenclature. The light band across the equator is the Equatorial Zone (EZ). The rest of the surface is broken into zones (light colored) and belts (dark colored). This drawing doesn't have all the labels. It only labels what's visible through most small telescopes. The features drooping from the NEB are called festoons. I've managed to see festoons with a long focus six Newtonian, but not with my smaller telescopes.

The Great Red Spot (GRS) appears as a disruption in the SEB. The GRS varies in color and contrast over the years. In the 2009 season I was unable to glimpse it with a long focus 60mm refractor, though I know others have seen the Red Spot with similar instruments in previous years. I have seen the Great Red Spot in previous years with a 6 inch f/5 Newtonian.

In addition to these features, you may be able to see dark bars in the NEB.

What Do You Need To View Jupiter?

Jupiter can be enjoyed with a variety of equipment. You can start with just a pair of binoculars. With these, Jupiter will appear as a very bright but unresolved object with up to 4 pin points of light nearby. These points of light are the Galilean moons: Io, Europa, Ganymede, and Callisto. If you look and count less than 4, the others are either behind Jupiter and blocked from view, or in front of Jupiter and lost in its glare.

Moving up to just a 60mm refractor of decent quality will show the darkening of Jupiter's polar regions, and at least 2 dark bands, the NEB and SEB. At powers above 100x you may well see additional bands, such as the NTB. You might see the Great Red Spot if it's on the visible side of Jupiter, but don't be surprised if even a 3 inch telescope can't show it sometimes.

You can see shadow transits on Jupiter with a 60mm telescope, though you may have to stare awhile until you see your first one. The shadows through a 60mm are very tiny dots. Through larger telescopes the shadows are still just dots, but they stand out better.

To get the best views of Jupiter, you might consider a long focus refractor of 60mm or larger. Significant detail can be seen with a 4 inch refractor. Refractors do well on Jupiter because the contrast between the zones and belts is not great, and refractors deliver the best contrast for any given aperture.

Maksutov telescopes, such as the Questar and Meade ETX series, do very well on Jupiter. The secondary mirrors of the Maksutovs cause them to have a bit less contrast than quality refractors of equal diameter, but Maksutovs are known for their crisp, chroma free images.

Next best are probably Newtonian telescopes of long focal ratios -- f/8 or better. I have a 6 inch f/10 Newtonian that delivers very good planetary images. The longer focal length Newtonians have flatter fields of view (no coma), less sensitivity to alignment, and smaller secondary mirrors that lead to better contrast.

Schmidt-Cassegrain telescopes can give good views of Jupiter also. These have larger secondary mirrors, which hurts contrast, but that can be made up for by using the larger sizes, like the common 8 inch SCT.

Even a shorter focus Newtonian telescope can deliver quality images. I've seen Ganymede as it traversed the surface of Jupiter, the Great Red Spot, and numerous moon shadow transits with my 6 inch f/5 Newtonian. It must be precisely aligned to perform well, but it can deliver an enjoyable show.

There are things you can do to improve your Jupiter viewing. Let your telescope cool down to ambient temperature before expecting it to deliver steady images. The time this takes is longer for bigger telescopes, and generally longer for reflector type telescopes. Don't observe over the top of nearby buildings. The heat rising from the buildings will cause significant image instability. If possible, observe when the planet is highest in the sky, rather than low to the horizon.

Try using a color filter on your eyepiece. Yellow is a common filter used to enhance the contrast of the Jupiter features. I generally use an apodizing screen on my 6 inch f/5. That apodizing screen helps reduce some of the light scattered by the secondary. That has the effect of slightly enhancing contrast.

If you need to get a telescope or observing accessory, try this custom search engine for your shopping.

Custom Search

The fun Jovian features are the Great Red Spot, festoons (if you can see them), bars in the NEB, and possibly some white spots in the latitude of the GRS. Certainly the positions of the moons are fun to track. The shadows of the moons can be seen when they move across the surface of Jupiter. The shadows may accompany their respective moon closely if Jupiter is near opposition, or greatly lead or lag the actual moon crossing, depending upon Jupiter's position with respect to the Sun.

On occasion, you can actually see a moon moving across the planet rather than its shadow. Seeing a moon image as it moves across the planet is quite difficult. The moons are bright, and so is much of the surface of Jupiter.

I have been able to see Ganymede move across Jupiter. On the occasion I saw it, Ganymede was moving across the polar area where Jupiter is darker, which made the moon just visible. I was observing on that occasion with a 6 inch f/5 Newtonian.

If you do a little planning and following some of these suggestions, I'm sure that you'll find Jupiter to be one of your most exciting observing targets.