Choosing Binoculars for Stargazing

These double-barrelled optical wonders will enhance your exploration of the night sky.

Binocular viewing

All photos courtesy Gary Seronik

Go out on the next clear night, and look up. You’ll see stars — lots of them, if you’re lucky enough to be far from city lights. You can spend many enjoyable hours learning star names and tracing out constellations using nothing more than the map that appears in the centre of every issue of SkyNews, a dim red flashlight (to protect your night vision) and a comfortable lawn chair. But eventually, you’ll probably want to delve a little deeper.

Welcome to the Binocular Universe

If you have never turned your binoculars skyward on a starry night, you might be surprised by how much they can reveal. Under a dark moonless sky, with your eyes alone, you can see perhaps 3,000 stars. But with binoculars, that number swells to 100,000 or more! Even better are the hundreds of star clusters, galaxies and nebulas that become visible in binoculars. And let’s not forget the sights closer to home. The Moon is transformed into a cratered wonderland, and you’ll be able to pull in the distant planets Uranus and Neptune and watch the nightly dance of Jupiter’s four biggest moons.

Binocular field of view

One of the big advantages binoculars have over telescopes is their ability to show a generous amount of sky and comfortably frame large subjects, as seen in this image of the Pleiades star cluster. Even a low-power telescope (orange circle) shows only a handful of stars, but binoculars (blue circle) show the cluster in all its glory.

Bino tripod adapter

A handy feature of many binoculars is a camera-tripod socket in the centre shaft. It is usually hidden by a screw-off plastic cap (not shown). The socket allows you to mount your binoculars on a tripod using an L-shaped binocular tripod adapter, available at well-stocked camera stores and all telescope dealers.

But, you may ask, if binoculars can do all that, wouldn’t a telescope be even better? Yes, but binoculars have important advantages over telescopes, especially if you’re just getting started. First, the view in binoculars has the same orientation as the world with which you are familiar: up is up, and down is down. Not so in most telescopes, where up is often down, and left is often right. Sure, there’s no up or down in space, but it’s tough finding your way around initially when reality is turned upside down or mirror-imaged. It really helps to keep things as straightforward and uncomplicated as possible when you’re beginning your exploration of the night sky.

A second, equally important binocular advantage is field of view, or how much sky you can see at a time. Try this experiment: Look through the cardboard tube from a roll of paper towels; now look at the same scene through a standard drinking straw. The difference in the views through the tube and the straw is about the same as the difference in the amount of sky you will see in ordinary binoculars and a small telescope. When it comes to wide-field views of the Milky Way and big deep-sky wonders, binoculars simply can’t be beaten. And that generous field of view also makes it much easier to find your target.

Almost any binocular will work reasonably well for exploring the night sky, so if you already own a pair, give them a try. That said, some binoculars are definitely better for stargazing than others. Walk into any well-stocked camera store, and you’ll be confronted with a bewildering array of binoculars with different features and specifications. Don’t panic. You can safely ignore most of the techno- babble. As long as you buy from a reputable dealer, you’re unlikely to encounter unusable junk. So let’s concentrate on the two factors that make the biggest difference in what you’ll be able to see: magnification and light-gathering ability.

Binocular specifications

The size of a binocular’s two main lenses and its magnification, which are usually stamped right on the binocular, characterize how well it will show sky sights. This particular mode magnifies eight times and features lenses 56 millimetres in diameter.

Decoding the Numbers

Binoculars are usually characterized by two numbers: 7×50 or 8×56, for example. The first number is the magnification; the second, the diameter of the front lenses in millimetres. A pair of 7×50 binoculars magnify seven times, making objects appear seven times closer, and have objective lenses that each measure 50 millimetres across. These two numbers are the key to choosing good astronomy binoculars.

Which combination of magnification and aperture is best? There isn’t a single “right” answer, and no matter which model you choose, you’re going to be making some trade-offs. Generally, more magnification means seeing more detail in sky objects. But as the power goes up, the amount of sky you see (the true field of view) goes down. Similarly, big objective lenses gather more light, allowing you to see fainter objects, but result in binoculars that are heavier and more difficult to hold and use.

Roy Bishop, the former editor of The Royal Astronomical Society of Canada’s Observer’s Handbook, devised a simple rule of thumb to help evaluate the relative performance of different binoculars: Simply multiply the aperture by the magnification. For example, 7×50s get a rating of 350, while 10×30s rate 300, suggesting that all other things being equal, the 10×30s will do almost as well as the bigger binos.

I usually recommend 10×50s as the near ideal compromise between capability and ease of use. But depending on your interests and circumstances, another combination might appeal to you more. Whichever model you decide on, be sure to try before you buy. It’s best to evaluate your binoculars by viewing the night sky, a more demanding optical test than daytime viewing. Good binoculars will produce sharp stars across most of the field (the edge of the field is usually blurry). Pay close attention to stars at the centre of the field—they should focus down to tiny pinpoints. Also check out the mechanical aspects of the binoculars. Do they feel sturdy? Do they focus precisely? Generally, higher-priced binoculars mean better mechanics and incrementally better optical quality.

Favourite binos

Binoculars come in many sizes and shapes. All can be used to explore the wonders of the night sky, but some perform better than others. Recommended models are (from front to back) the Canon Image-Stabilized 10×30, Orion Resolux 10×50, Celestron Ultima DX 8×56 and Bushnell Astralis 15×70.

A Few Favourite Binos

Over the years, I’ve looked through countless binoculars and amassed an embarrassingly large collection. Here are a few of my favourites. Each has its strengths and weak- nesses, but I can recommend them all with- out hesitation.

Canon Image-Stabilized 10×30: I’ve written reviews  of every member of Canon’s line of image-stabilized binoculars (ISBs). ISBs use a combination of optics and electronics to cancel out the jiggles that accompany handheld viewing. The effect is magical. In my opinion, Canon’s 10×42 ISBs are the finest astronomy binoculars currently available. Unfortunately, they cost more than $1,000. For around $400, however, you can get the 10×30 version — the lowest-priced, astronomically useful binos in the Canon ISB line. The 10×30s are lightweight (approximately 1.4 pounds) and have excellent optics  that yield a sharp, true field of six degrees. These binoculars are great all-rounders. Indeed, when I’m heading out for a day of birding or a night of stargazing, it’s my 10x30s I reach for most often.

Orion Resolux 10×50: Good 10x50s are nearly ideal all-purpose astronomy binoculars, and the Resolux model from Orion Telescopes and Binoculars are good. They’re ruggedly built, rubberized and water- proof. Optically, they’re very nice. The lens coatings are first-rate, and the wide-angle eyepieces provide expansive views. Be warned, though: These binoculars are heavy for their size, weighing in at 3.4 pounds, and a tripod mount is highly recommended.

Celestron SkyMaster 8×56: If your budget doesn’t allow for image-stabilized binoculars, this pair from Celestron is a very good choice. They’re light enough (2.3 pounds) to deliver good images even when handheld, and the views are bright and clean, thanks to the 56mm objective lenses and effective optical coatings. They also provide a generous 5.8-degree field of view, second only to the 10×30 Canon binos. (These binoculars are available directly from SkyNews.)

Bushnell Astralis 15×70: The optics in these big binoculars are so-so. The coatings are OK, but not the best. Mechanically, they feel a bit flimsy and require frequent refocusing. So why do I recommend them? Simply because they provide the most detailed views of any binocular on my list. The combination of 15× magnification and 70mm aperture — even in a mediocre binocular — shows more than do smaller high-quality binoculars. And this performance comes at a budget price. I bought mine at a local camera store for $130. (Virtually identical versions are also available from Celestron and other brand names.) If you go the cheap-and-cheerful route, though, be sure to buy from a dealer with a good return policy, just in case there’s a problem. And expect to use a tripod. You simply can’t get the most out of these binos when they are handheld.

When choosing binoculars, don’t forget they are merely a tool — it’s what you can do with them that matters. It’s easy to get caught up in specifications and optical perfection and lose sight of the point. Indeed, good binoculars don’t call attention to themselves by demanding constant adjustment or tiring your arms or eyes. Remember, it’s all about what you see, rather than what you see it with.

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