The key is: Exit pupils should roughly match your eyes' pupils. And eyes change with age. As a middle-age person, my dark-adapted eyes open to a pupil diameter of about 5 mm. A year-old child's pupils can open much wider, to almost 8 mm. Lower power binoculars — which tend to be smaller — usually produce larger exit pupil diameters that literally won't fit into my eyes! Take this into account if you're buying binoculars as an adult. Purchasing for someone a bit younger?
Have a look through our guide to the best binoculars for kids. Interestingly, older folks may have more disposable income for the more expensive higher-power instruments. But, to make sure you're spending your money wisely, check the shape of those exit pupils, floating there in the eyepieces: They should be flawlessly round. Also make sure you have access to dark skies. As magnification goes up, apparent brightness of the image goes down. Poor optical design can hack off the sides and you will see this clearly, if you can hold the actual binoculars in front of you.
If shopping on the Internet, you'll have to pick a brand with a decent reputation, or trust a review like ours. If you are reading this, you no doubt have noticed there are many different configurations on the market. One size definitely does NOT fit all. Some skywatchers prefer strong magnification to resolve the thousands of light-points within dense star clusters , and to pick out fine structure within galaxies.
Others opt for a wide-field, immersive "space-walking" experience, preferring low-mass portability to power. Like sports cars or yachts, there's a tendency to want to own the more powerful thing. Certainly, there're some impressively large — "gotta use 'em on a tripod" — monster binoculars on the market.
And as we age, there may be good reasons to dial up the magnification a bit more on this later. I believe the best binoculars are the ones you have with you. Meaning: Buy the pair you'll be most likely to take on your travels more often, whether you're going out into the backyard or across the planet. That implies a smaller and lighter form factor, which tends to be lower power. If this is your only pair, I'd suggest an objective no larger than 50 mm the number after the "x," as in 7x40 , and a magnification no bigger than 10x.
Really, you'll be OK with even smaller binoculars, as long as they are of high-quality optical glass. You can carry an 8x35 pair all day for bird- or people watching, and they won't make your arms tremble — and your stars dance like drunkards — when you pick them up at night.
The wider view-field of most lower-power binoculars is usually a plus for skywatching. Meteor showers offer a practical example. You never know exactly where the next bright streak will appear. Yes, you're pretty sure it will come from the "radiant. But, in practice, the radiant is an area at least 10 degrees across. You will spot more meteors with a wider field of view.
So think carefully about size, weight and stars turning into wiggly lines before you go big. Don't expect telescope companies' marketing pitches to tell you this. We live on the Water Planet. If you've got an ordinary pair of binoculars lying around, astronomical observing is just a clear night away. Beginning stargazers often overlook binoculars for astronomy, but experienced observers keep them close at hand. Compared to a telescope, binoculars for astronomy actually have certain advantages.
Granted, they're smaller and give lower magnification. But they're lighter, much easier to take outside, use, and put away, and less expensive. They also give a much wider view than a telescope does, making celestial objects easier to find. They let you use both eyes, providing surer, more natural views.
Finally, there's another big plus for binoculars: you may already have a pair in the back of a closet or know someone who can loan you a pair.
If so, stop reading and go get them now. I'll wait. Now look them over. On the back you'll see two numbers separated by an "x". Common combinations are 8x40, 7x35, 7x50, and 10x The first number is the magnification , or "power. You may also find more numbers below the magnification-x-aperture rating. These give the field of view , which is how wide a scene you'll see.
It's expressed in feet at a distance of 1, yards, or, more commonly these days, in degrees. No matter what binoculars you just dug out of the closet, they'll be a great addition to your stargazing sessions.
Consider this: on a clear, dark night out in the country, your eyes can see up to 3, stars, give or take. But when you use even modest 7x35 binoculars, that number rises to roughly , stars! Similarly, in a light-polluted suburb you may be able to see only a couple hundred stars unaided, but binoculars for astronomy will cut through the murk to show you more than you could see with your unaided eye from the top of Mount Everest.
There's much more to look at in the night sky than random stars. Scores of double stars, rich Milky Way star clouds, star clusters of various sizes and types, stars that vary in brightness from month to month or even hour to hour, a smattering of ghostly nebulae and dim, distant galaxies — all are waiting for you to track them down with binoculars and suitably detailed sky maps and guidebooks. In Binocular Highlights , you'll get a detailed guide to 99 celestial delights — from softly glowing clouds of gas and dust to unusual stars, clumps of stars, and vast galaxies — all visible in binoculars for astronomy, and most visible even from light-polluted skies!
Granted, most of the interesting astronomical objects that binoculars can show will appear very faint in them. But most objects that a telescope will show also appear very faint in it — certainly much fainter than you would like. Moreover, the map-using skills that you'll gain using binoculars to hunt out these dim, distant things in the dark wilds overhead are exactly the skills that you will need in order to put a telescope to good use.
And the sky is always changing. Summertime offers such showpiece sights as Mizar and Alcor, the famous pair of stars at the bend in the Big Dipper's handle, and the perfectly round little fuzzball of M13, the Great Cluster in Hercules. Sweep the summer Milky Way from Cygnus overhead through Sagittarius low in the south, looking for knots of stars and luminous bubbles of interstellar gas.
Some sections of the Milky Way look, to me, better in binoculars for astronomy than through any telescope.
In autumn, don't miss the Great Andromeda Galaxy, which looks like a dimly glowing little oval cloud. Contrast its smoothness with the delicate sparkle of the Double Cluster in Perseus. Winter's crisp skies are great for scanning the Hyades and Pleiades star clusters, then sweeping down to gaze at the Great Orion Nebula in Orion's Sword.
Spring brings the unique Beehive star cluster in the constellation Cancer. If you don't already have binoculars or if you're outgrowing the ones you've got , it's time to buy. But there are so many choices. Are some better for astronomy, as opposed to birdwatching or baseball games? You bet! Astronomy is done in the dark, so you really want big aperture: big front lenses.
These collect lots of light so you can see fainter things. This doesn't matter so much in the daytime, when there's plenty of light and you can get by with small front lenses — allowing daytime binoculars to be smaller, lighter, and less expensive. But for binoculars for astronomy, the bigger the aperture the better. You cannot handhold at magnifications above about 10X; the image gets way too jumpy, so you need a mount, like a tripod.
The tiny field of view means you now also need a way to precisely navigate and track your target as the Earth rotates. Such a mount costs as much as the telescope itself.
For most scientific projects, a single point of view is all that is needed, so astronomers overwhelmingly use a telescope. But for exploring the sky with your own two eyes, the priority is a large field of view.
To sweep the magnificent star fields of the Milky Way, or spot the eerie glow surrounding baby stars in the Orion Nebula, binoculars are a great choice. They are compact, portable and need no mount. Get the biggest objective lenses you can 50 mm or more and keep the magnification low 10X or less. This article is republished from The Conversation under a Creative Commons license. Read the original article. Receive news, sky-event information, observing tips, and more from Astronomy's weekly email newsletter.
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Login or Register Customer Service. RISE —. PHASE —. Tonight's Sky — Change location. US state, Canadian province, or country. Tonight's Sky — Select location. Tonight's Sky — Enter coordinates. UTC Offset:. The first thing beginners look at through their new binoculars is almost always the Moon. The best binoculars for stargazing balance magnification with letting as much light in as possible.
For beginner stargazers the ideal combination is a low magnification of around 7x to 10x and an aperture of about 42mm to 50mm. Binoculars with these specifications — expressed as 7x42, 10x50 or similar combinations — are small and light enough to hold reasonably steady. They also give a wide enough field of view of the night sky and create a bright image in darkness. Our favorite pair of binoculars are the Celestron TrailSeeker 8x Other technical features to look out for are Porro prisms, multi-coated optics and barium crown BAK4 glass.
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