This is our guide to help you see Jupiter in a small telescope. If you own a scope of 6 inches or smaller, then keep reading to learn how to find Jupiter and what you should aim to observe.
Jupiter is a massive planet. In fact, it’s the biggest in the solar system by quite some margin. Jupiter has more than twice the mass of Mercury, Venus, Earth, Mars, Saturn, Uranus, and Neptune combined.
So, even though it is much further away from us than Mars, it appears much more significant in our telescopes, even when Mars is at its closest approach.
The difference is stark. At Mars’ closest approach, which happens every two years, the red planet has a maximum angular diameter of 25.1”. In contrast, Jupiter never appears smaller in our sky than 29.8”.
When Jupiter reaches opposition, its disc can reach a diameter of 50 arcseconds. When you are on the hunt for smaller details, it pays to look at opposition because the planet is up to 60% larger than when at its most distant.
This is all excellent news for those of us who own a smaller telescope because that big disc is bright enough to show us super details. Throw in Galilean moons and vibrant surface features, and you’ll see why many backyard astronomers think of Jupiter as the ‘goto’ planet of choice.
How to Find Jupiter in the Night Sky
Being so bright, Jupiter is very easy to find with the naked eye when it is visible. Follow the steps below to work out where to look.
Step 1 – Is Jupiter in the Night Sky Tonight?
Like most celestial objects, Jupiter spends part of the time unobservable because it is below the horizon during the hours of darkness. So, before setting out to view it, you need to know it is actually in tonight’s night sky.
For a quick reckoner, use our guide to where the planets are this month.
To use Stellarium, set the time you plan to observe and your location. Next, search for Jupiter and the planet will be centered in your viewing window.
For Sky Safari the process is even simpler.
Use the search box to select and locate Jupiter. When you have it, press the ‘i’ button for information about the planet.
In the list to the left of the screengrab below, you’ll see rise, transit and set times for your location. There’s a whole host of other information that we’ll use later too.
Once you know Jupiter is visible, we need to find it.
Step 2 – Finding Jupiter Without a Telescope
As we said earlier, Jupiter is big and bright. It’s actually the third brightest object in the sky, after the moon and Venus, which makes it very easy to see with the naked eye.
Start your viewing adventure doing exactly that, finding Jupiter with your naked eyes. Use the sky plan from your software, or the monthly guide from Sky & Telescope Magazine (Amazon link) to help you locate it.
In the screengrab below, from Sky Safari 6, you can see that Jupiter is almost 12.5° above the southeast horizon.
Remember, the horizon is 0° and directly overhead is 90° and midway between the two is 45°. If you’re not sure on angles, use these hand shapes to make it easier.
Even when you look in roughly the right place, Jupiter will always be the brightest ‘star’ you can see (unless Venus happens to be close by).
Step 3 – Finding Jupiter with a Small Telescope
Now we turn to the good bit: seeing this massive gas giant through your telescope.
Although the planet will stand a good deal of magnification, it’s best to start with lower levels. This increases the field of view which makes it easy to get the planet in sight before you begin to zoom in and study more details.
Assuming you have correctly set up your finderscope, all you do to get Jupiter in view is center your finderscope on the bright ‘star’ you identified in step 2.
A glimpse in your eyepiece will quickly show whether you have a planet in view. Unlike stars, which all stay as tiny pinpricks of light, Jupiter is distinctly disc-shaped. Move your focuser to get the planet in sharp focus.
Finally, make a quick check to see you have Jupiter and not another planet.
Even in the smallest scopes, up to four tiny pinpricks of light can be seen in a straight line with Jupiter. They may all be on one side, but they are more likely to split either side of the planet.
If you see these, you definitely have Jupiter in view because those tiny dots are the Galilean moons, which we’ll look at in more detail, below. Watch the video below at about 30 seconds in to see what the moons look like either side of Jupiter.
The other big giveaway is that you’ll probably notice at least two or three darker bands crossing the face of the disc in your eyepiece. If you do, you are centered on Jupiter, and it’s time to take a closer look.
Three Targets when Observing Jupiter With a Small Telescope
Now you have Jupiter in the eyepiece of your small telescope, what should you be looking at?
Well, there are three great targets for you to try and tease out. The first is the Galilean moons. These are easy enough to be seen with the smallest of scopes.
Secondly, turn your attention to the planet itself and aim to distinguish the major zones and bands we find there. The most apparent bands are visible in smaller scopes, but darker skies and larger objective lenses will reveal more details and thinner bands.
Finally, the hardest challenge of them all is to see the infamous Great Red Spot.
We’ve given you more detail and resources for each below.
Target 1: How to See Jupiter’s Galilean Moons
There are four Galilean moons. In order from closest to the planet, outwards, they are Io, Europa, Ganymede, and Callisto. Each of these moons is large – they are all bigger than Pluto – which is why we can see them clearly from this distance.
Their size is also partly the reason for their name. They were bright enough to be spotted by the infamous scientist Galileo Galilei when he first pointed a telescope skywards back in 1610.
Each of the moons orbits Jupiter. The closest of the four, Io, orbits faster than the next closest, Europa and so on to Callisto which takes the longest time to complete its Jovian circuit.
The orbital periods of the Galilean moons are:
- Io – 42 hours
- Europa – 3.5 days
- Ganymede – 7.2 days
- Callisto – 16.7 days
This dynamic arrangement of the moons is the first observing challenge for your small scope.
Armed with this month’s Jupiter almanac from Sky & Telescope magazine, or using your favorite astronomy software, identify the moons visible to you in the eyepiece. The screen grab below shows what this looks like in Sky Safari.
Check back just hours later to see noticeable movement in Io’s position and a day or two later to see changes in all of the moons.
Many astronomers like to extend their Galilean moon observation into seeing transits and and occultations, i.e., when they will pass either in front of or behind the planet from our perspective.
Use an almanac like this one to get timings for such events. Keep in mind that observing events like these is made easier with a bigger scope and dark skies. Note also that it’s easier to see the moon’s shadow crossing the planet’s surface than the moon itself, which is why we have ‘shadow crossing’ times as well as moon transits.
Target 2: Seeing Bands and Zones on Jupiter’s Surface
After having observed the Galilean moons, it makes sense to move on the most noticeable features on the giant planet’s surface: its cloud bands.
Actually, the lines of division on the surface are of two different kinds. The dark areas are called bands and lighter ones zones.
There are 15 distinct bands and zones according to the image below, but not all of these will be visible in your scope.
Because Jupiter is big and bright, don’t be afraid to push the magnification of your scope when trying to spot the different belts and zones.
If you haven’t already done so, swap your eyepiece for one that gives more magnification, i.e., one with a smaller number. A 10mm eyepiece, for example, provides greater magnification than a 20mm eyepiece.
Make the changes gradual if possible, so you maintain a good feel for the planet as you view it. Don’t jump from 30mm to 9mm eyepieces, go from 30mm to 20mm, to 15mm and then to 9mm (using the eyepieces you have available, of course).
Making changes this way, you’ll be able to tell which of them gives you the best balance between magnification and image quality. All telescopes, but especially smaller ones, lose image quality as magnification climbs. Magnification is not much help if the image quality is too weak to make out details!
At the very least, you should be able to distinguish the lighter equatorial zone (EZ on diagram) when compared to the north and south equatorial bands (NEB and SEB). You should also have no difficulty picking out the north and south polar regions (NPR and SPR).
What you can see beyond that depends very much on the quality and size of your telescope and how good the seeing is.
Target 3: Seeing Jupiter’s Great Red Spot with a Telescope
Before we try for the Great Red Spot (GRS), look at the disc of Jupiter itself.
Can you see that it’s not quite spherical? See that it’s fatter in the middle (equator) like a squashed ball. That comes about because the planet spins so quickly on its axis. Our own earth, tiny in comparison, spins at 1,000 mph at the equator giving us a 24hr day.
Giant Jupiter spins at 28,000 mph at the equator and takes less than half the time to rotate once on its axis. A day on Jupiter is only 9.5 hours long!
We mention this because that’s how often the GRS spins around the planet too. At least twice per [Earth] day, the Great Red Spot faces us. All we need are its timings and a telescope with the capability to see it.
Getting hold of GRS transit times is straightforward enough. Sky Safari, for example, displays it when you click on the information button ‘i’ when you have Jupiter selected.
You can also make use of the raw data on the Project Pluto website, which is not as pretty but is free and perfectly accurate. Just remember all times are given as Universal Time (UT) so you’ll need to adjust for your local timezone. You can get good views of the GRS up to an hour before and after the transit times given.
With the timings sorted, you’ll need to know if your telescope can resolve the Great Red Spot in the eyepiece.
Honestly, seeing the GRS in a smaller telescope is quite a challenge. Even though this raging storm on Jupiter’s surface is twice the size of Earth, its distance from us makes it a tiny object to discern.
Great seeing conditions and a very dark night are must-haves.
After that, you’ll need to make use of at least 100x magnification and probably >150x to have a chance of seeing it. The very best opportunities come when Jupiter is at opposition because it is closer, giving a much larger target for us to see.
Jupiter oppositions happen every 13 months or so, the next few occur in June of 2019, July 2020, August 2021 and September 2022.
To further improve your odds of seeing the GRS, try a green filter to make the spot appear darker against the background of the planet. Filter #56 and #58 are suitable.
The final piece of advice when hunting for the spot? Don’t give up!
Even if you are looking at the right time and have good seeing, it can take some time to tease out the spot. Remember to use averted vision and rest your eyes every few minutes to maximize your spotting chances.
Jupiter is the largest planet in our solar system which makes it an excellent target for backyard astronomy with a small telescope.
Couple that enormous girth with an engaging surface and dynamic, bright moons and there is a lot for us to get excited about.
With a small telescope, you will see the Galilean moons and at least the most prominent belts and zones on the Jovian surface. A slightly larger scope of, say 4”-6” will give you the chance to see the Great Red Spot under excellent conditions.
As soon as Jupiter is out again on a moonless night, point your scope its way and see what you can discover.