Exploring the Planets With an Amateur Telescope

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7 Things to Consider Before Buying a Telescope

For telescope owners, the whole sky is a playground. Most people have their favourite targets, including the planets. The brightest ones stand out in the night sky and are easy to spot by the naked eye and can be studied through a scope.

There’s no “one size fits all” solution to planet-gazing, but it’s important to get the right telescope to observe other worlds in the solar system. In general, small telescopes (three inches or smaller) with low magnification will not show as much detail as larger amateur telescopes at higher magnification. (Magnification is a term that means how many times larger a telescope will make an object look).

Setting Up the Scope

Practice setting up the telescope before use.
Andy Crawford/Getty Images

With a new telescope, it’s always a very good idea to practice setting it up inside before taking it outdoors. This allows the scope owner to get to know the instrument without fumbling around in the dark to find set screws and focusers.

Many experienced amateur observers let their scopes get used to outside temperatures. This takes about 30 minutes. While the equipment is cooling down, it’s time to gather star charts and other accessories, and put on some warm clothes.

Most telescopes come with eyepieces. These are small pieces of optics that help magnify the view through the scope. It’s always best to check the help guides to see which one is best for planetary viewing and for a given telescope. In general, look for eyepieces with names like Plössl or Orthoscopic, in lengths of three to nine millimetres. Which one an observer gets depends on the size and focal length of the telescope they own.

If this all seems confusing (and it is in the beginning), it’s always a good idea to take the scope to a local astronomy club, camera store, or planetarium for advice from more experienced observers. There’s a wealth of information available online, too.

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winter hexagon
Carolyn Collins Petersen

It’s important to research which stars will be in the sky at any given time. Magazines such as Sky & Telescope and Astronomy publish charts each month on their websites showing what’s visible, including the planets. Astronomy software packages, like Stellarium, have much of the same information. There are also smartphone apps such as StarMap2 that provide star charts very quickly.

Another thing to keep in mind is that we all view the planets through Earth’s atmosphere, which can very often make the view through the eyepiece look less sharp. So, even with good equipment, sometimes the view isn’t as great as people would like it to be. That’s a feature, not a bug, of stargazing.

Planetary Targets: The Moon

Viewing the moon in a telescope.
Tom Ruen, Wikimedia Commons.

The easiest object in the sky to observe with a telescope is the Moon. It’s usually up at night, but it’s also in the sky during the day during part of the month. It’s a great object to photograph as well, and these days, people are even using their smartphone cameras to shoot great images of it through a telescope eyepiece.

Nearly every telescope, from the smallest beginner equipment to the most expensive amateur one, will give a great view of the lunar surface. There are craters, mountains, valleys, and plains to check out.

Venus

Venus in one of its phases.
US Naval Observatory

Venus is a cloud-covered planet, so there’s not a lot of detail that can be seen. Still, it does go through phases, as the Moon does. Those are visible through a telescope. To the naked eye, Venus looks like a bright, white object, and is sometimes called the “Morning Star” or “Evening Star,” depending on when it’s up. Usually, observers look for it right after sunset or just before sunrise.​​

Mars

Viewing the planet Mars through a 4" telescope.
Loch Ness Productions, used by permission.

Mars is a fascinating planet and many new telescope owners want to see details of its surface. The good news is that when it’s available, it’s easy to find. Small telescopes show its red colour, its polar caps, and the dark regions on its surface. However, it takes stronger magnification to see anything more than bright and dark areas on the planet.

People with larger telescopes and high magnification (say 100x to 250x) might be able to make out clouds in Mars. Still, it’s worth the time to check out the red planet and see the same views that people like Percival Lowell and others first saw at the beginning of the 20th century. Then, marvel at the professional planetary images from such sources as Hubble Space Telescope and the Mars Curiosity rover.

Jupiter

Jupiter through a four-inch telescope.
Loch Ness Productions, used by permission.

The massive planet Jupiter offers observers a lot to explore. First, there is a chance to see its four largest moons fairly easily. Then, on the planet itself, there are amazing cloud features. Even the smallest telescopes (less than 6″ aperture) can also show the cloud belts and zones, particularly the dark ones. If small scope users are lucky (and seeing conditions here on Earth are good), the Great Red Spot might be visible, too. Folks with larger telescopes will definitely be able to see the belts and zones in greater detail, plus a better view of the Great Spot. For the widest view, though, put in a low-power eyepiece and marvel at those moons. For more details, magnify as much as possible to see the fine details.

Saturn

viewing saturn through a backyard telescope
Carolyn Collins Petersen

Like Jupiter, Saturn is a “must-see” for scope owners. That’s because of the amazing set of rings it has. Even in the smallest telescopes, people can usually make out the rings, and they might be able to make out a glimmer of the cloud belts on the planet. However, to get a really detailed view, it’s best to zoom in with a high-powered eyepiece on a medium to​ a large-size telescope. Then, the rings really come into sharp focus and those belts and zones come into better view.

Uranus and Neptune

Finding Uranus and Neptune to view through a small telescope.
Carolyn Collins Petersen

The two most distant gas giant planets, Uranus and Neptune, can be spotted through small telescopes, and some observers claim they’ve found them using high-powered binoculars. Very few (if any) people can see them with the naked eye. They’re just too dim, so it’s best to use a scope or binoculars.

Uranus looks like a little blue-green disk-shaped point of light. Neptune is also bluish-green, and definitely a point of light. That’s because they’re so far away. Still, they’re a great challenge and can be found using a good star chart and the right scope.

Challenges: The Larger Asteroids

Star charts help observers find asteroids and minor planets, too.
Carolyn Collins Petersen

Those lucky enough to get good-sized amateur scopes can spend a lot of time searching out the larger asteroids and possibly the planet Pluto. It takes some doing and requires a high-power setup and a good set of star charts with asteroid positions carefully marked. Also check astronomy-related magazine Websites, such as Sky & Telescope Magazine and Astronomy Magazine. NASA’s Jet Propulsion Laboratory has a handy widget for dedicated asteroid searchers that gives updates on asteroids to watch out for.

The Mercury Challenge

A sample star chart for finding Mercury.
Carolyn Collins Petersen

Planet Mercury, on the other hand, is a challenging object for another reason: it’s so close to the Sun. Ordinarily, no one would want to point their scope toward the Sun and risk eye damage. And no one should unless they know exactly what they’re doing.

However, during part of its orbit, Mercury is far enough away from the Sun’s glare that it can be safely observed through a telescope. Those times are called “greatest western elongation” and “greatest eastern elongation”. Astronomy software can show exactly when to look. Mercury will appear as a dim, but a distinct dot of light either right after sunset or before sunrise. Great care should be taken to protect the eyes, even at times when the Sun is already down.

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