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Hi- To all and sundry-
Sorry I haven’t posted for so long, a combination of illness in the family and new work responsibilities have hit me hard. But… I have some new items I want to add in the next weeks to bring more helpful information on where to find great accessories for telescope binoculars. So stay tuned..
(This is the final installment of this terrific article. Many thanks again to Ed Ting for permission to serialize his article here. I think it’s mandatory reading for anyone who is considering telescope binoculars for astronomy viewing. Ted)
Keep It Simple
Let me offer one final caution: Keep it simple. As a rule you should avoid zoom binoculars, at least for astronomical use. Good zoom eyepieces require a very high (and expensive) standard of precision manufacture that’s usually not met.
Likewise, binoculars with built-in cameras may be okay for casual daytime use, but not at night. They’re gimmicky toys.
Most binoculars have center focus, meaning that you focus both barrels at once by turning a knob or a rocker in the center. This is great for when the distance of your target often changes, such as in birdwatching, or when you often pass the binoculars back and forth between people. But the night sky always stays at infinity focus, and you’re probably observing it alone. So eyepieces will do just fime. This not only saves you money but provides better mechanical stability and gets rid of a common cause of eyepiece misalignment (slight tipping of the center-focus mechanism).
But no matter what imperfections you have to live with (and face it, optical perfection does not exist), you’ll find that binoculars can show you more of the universe than you probably imagined.
(Note: I want to thank Ed Ting again for his permission in reprinting this thorough primer on starting with Binocular Astronomy. Based in Amherst, New Hampshire, Ed Ting reviews stargazing equipment for his website, www.scopereviews.com. This article appeared previously in Sky and Telescope.com.
For a great selection of telescope binoculars for astronomy viewing, please visit our site and check out our astronomy binoculars Ted)
(Thanks to Ed Ting for permission to serialize his article here. I think it’s mandatory reading for anyone who is considering telescope binoculars for astronomy viewing. Ted)
Next, if you wear glasses for astigmatism, make sure you can see the entire field of view with your glasses on. If you’re merely near-sighted or far-sighted, you can observe with your glasses off and just refocus as needed. If you’re astigmatic, sorry — you’ll have to use the binoculars with your glasses on, so this test will be important.
Next: see if you can detect whether the binoculars’ two barrels are out of optical alignment, or “collimation.” Experienced users can pick up on this relatively quickly, but beginners have a harder time of it, because your eye and brain automatically try to compensate for any misalignment. The best way I can describe this is that out-of-alignment binoculars will make you feel slightly “seasick.” In really bad cases you may have trouble merging the two images into one, at least right away. Or maybe you’ll have a mild sense of relief when you stop looking through them. Reject such units.
Finally — at last! — look through the binoculars.
Notice the size of the field of view: the wider the better. But the edges of a wide field may have poor optical quality. Is the view near the edge blurry when the center is sharp? Some binoculars are much better in this regard than others.
Sweep the field at right angles across a straight line, such as a door frame or a telephone wire. Watch whether the line bows in or out near the edges. This distortion should be only slight.
Look at sharp lines dividing light and dark, such as dark tree limbs or the edge of a building against a bright sky. Do they have red or blue fringes? No instrument is perfectly free of this chromatic aberration, but some are better than others.
Follow these steps and you’ll go a long way toward selecting quality binoculars right there in the store. If you’re ordering from an online or mail-order distributor, this kind of test drive won’t be possible before you make the purchase. So make sure the sales policies allow you to return defective or unsatisfactory units, then check the pair thoroughly once they arrive. (Note: At Telescope Binoculars we have lifetime guarantees on virtually all our binoculars. We work directly with the manufacturer and will ensure that – in the highly unlikely event of defective workmanship – you are completely satisfied with your binoculars and our service. Ted)
(Thanks to Ed Ting for permission to serialize his article here. I think it’s mandatory reading for anyone who is considering telescope binoculars for astronomy viewing. Ted)
Testing Binoculars
Of course, the best way to see if a telescope binoculars model suits you is to give it a good tryout at night. Do stars focus down to pinpoints better in one pair than another? Your local optical shop, however, may not be thrilled with the idea of letting you play with lots of equipment overnight on a loaner basis.
Luckily there are ways to tell right in the shop how well binoculars will likely perform. These tests really work (I’ve done them for years), and if you learn them well you’ll gain a reputation as an expert on binocular optics. Ready?
First, pick up several binoculars and look at their objective (front) lenses. Do this with a bright white light coming over your shoulder from behind. You’ll notice right away that in some objective lenses, the reflection of the light will be brighter than in others. Pick the models with the reflections that look darkest (and no doubt deeply colored); this is a sign of quality lens coatings. Good coatings increase the transmission of light through the glass and reduce the amount of scattered light hazing the view.
Now, while still looking in the big front lenses, tilt the binoculars around a bit and look for more reflections deeper inside. They should all be colored, not white. A white reflection is the sign of a glass surface that has no coating at all.
You might think you could tell the quality of the coatings from designations such as “coated,” “multicoated,” or “fully multicoated,” but in practice these terms can be next to meaningless. The proof is in the looking, so look. (Note: Don’t be taken in by models hyping “ruby-coated lenses.” All our Barska models have fully multi-coated lenses.)
Now turn the binoculars around and repeat the procedure, looking for colored versus white reflections in the eye lenses.
Next, face well-lit wall and hold the binoculars nearly at arm’s length, with the eyepieces pointed at you. You’ll see the exit pupils (disks of light) floating just behind the eyepieces, as was illustrated above. You might think that exit pupils would always be perfectly round, but this isn’t so. The ones on cheaper binoculars often have a slightly “squared off” look, as if someone shaved off, or dimmed, two or four edges. This is a sign of manufacturer’s corner-cutting that will slightly dim all the images you see.
Pick the units with round exit pupils; this tells you that quality prisms were used and that you’re getting all the light you should. (You can also check the specification sheet: the best prisms are made from BAK-4 glass, while others use BK-7 glass.) Since they’re hidden inside, the prisms are one of the first things manufacturers skimp on when trying to lower the price. Seeing “shaded” or “squared off” exit pupils is a sign of lesser-quality or undersized prisms. (Note: See our spec sheets – our astronomy binoculars feature BAK-4 glass and a host of other quality features for a great optical experience.)
(Thanks to Ed Ting for permission to serialize his article here. I think it’s mandatory reading for anyone who is considering telescope binoculars for astronomy viewing. Ted)
Another recent innovation is image-stabilized binoculars. These employ the same ingenious mechanisms found inside the best video cameras. Push a button and the shaky magnified view suddenly calms down, almost freezing in place. The result is that you can use higher magnifications, get away with slightly less aperture, and yet still see more than with conventional binoculars.
I was skeptical when these little marvels were introduced, but I was quickly won over. When I first used Canon’s compact little 10×30 image-stabilized binoculars (shown at left) from a dark-sky site, I had no trouble picking out the galaxies M81 and M82 near the Big Dipper. In fact, I actually tried to jiggle the view, but it refused to budge!
You may be thinking that more magnification is better, but in practice once you get to 10x and above, it gets harder (and more tiring) to hold binoculars steady if they’re not on a mount or equipped with image stabilization.
There’s some debate on what magnification is best. Low-power advocates recommend staying with 7x or 8x, whereas the high-power types say that the increased detail and darker sky background provided by 10x units are worth the narrower field of view and extra jiggling.
My take on this? I’m in the low-power camp. I don’t find the visual difference between 7x and 10x all that great, but I’m noticeably less fatigued when using low-power glasses. If you get the chance, give both a good try and see which you prefer.
A related consideration is the exit pupil, the size of the little round disk of light that you see floating in the air behind the eyepieces when you hold the binoculars out in front of you toward a bright sky or a bright indoor wall. The size of the exit pupil is an important factor that’s often overlooked. To determine it, just divide the aperture by the magnification — and luckily these are inscribed right there on the back facing you. For example, 7×50 binoculars have about a 7-mm exit pupil, while 10×50s have a 5-mm exit pupil.
Why is this important? Because the bright disk of the exit pupil should fit inside the pupil of your eye. And not everyone’s eyes open to the same diameter in the dark. Young people (under age 30 or so) have pupils that open to about 7 millimeters across. While individuals vary a lot, the rule of thumb is that after age 30 you lose 1 mm of exit pupil every 10 or 15 years. So older eyes can’t take advantage of binoculars with large exit pupils and, as a result, might see no difference between 7×35s and 7×50s. The extra light collected by the bigger 7×50s isn’t fitting into your eyes; it’s just going to waste. Score a big point for the high-power camp, at least if you’re getting on in years; the higher the power, the smaller the exit pupil.
(Note: Our large Barska astronomy binoculars, like all of our telescope binoculars for astronomy, when used with a tripod or stabilized in another way, will give you the closest experience to a telescope you can get, with top quality optics. Ted)
(Thanks to Ed Ting for permission to serialize his article here. I think it’s mandatory reading for anyone who is considering telescope binoculars for astronomy viewing. Ted)
Buying Binoculars for Stargazing
If you don’t already have astronomy 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 astronomy, the bigger the aperture the better.
You also want high optical quality. Stars and faint celestial objects seen against a dark sky are much more demanding than daytime scenes, so mediocre optics display their flaws much more obviously when you’re observing the night sky rather than eatching the pitcher’s mound. In general, price is a pretty good indicator of optical quality. The best optics are not going to be cheap.
Binoculars come in two body styles: the familiar “stepped” look of the Porro-prism design (right), and the sleeker “H” profile of the roof-prism design (below right). Most binoculars marketed for astronomy use Porro prisms, named for the Italian optician who invented them in the 1850s.
Roof-prism units are smaller and lighter-weight but have a more complicated, touchy optical design, which makes them more difficult and expensive to manufacture well. As a result, roof-prism binoculars tend to cluster at the high end of the market and, inexplicably, at the bottom end too — but not so often in between. A saying around my local astronomy club is that if your roof-prism binoculars don’t seem to be performing well, you didn’t spend enough money!
In recent years there’s been a new twist on the bigger-is-better theme: giant telescope binoculars. These are impressive, even imposing-looking devices. It’s as if someone put your friendly 7×50s on steroids. Common apertures include 70, 80, and even 100 mm. (Fujinon even makes a 150-mm model — the equivalent of two 6-inch telescopes, one for each eye!) For such beasts a tripod, preferably with a special binocular mount that allows you to aim upward, is mandatory. While they’re a good supplement to your gear collection, I don’t recommend giant binoculars as your primary instruments — they’re just too unwieldy. Get more modest 7×40s or 10×50s first, and consider buying these big shots later.
(Note: This decision rests on how you use the binoculars – if you will use your car to get where you want to stargaze – go for the big ones. If you want them for camping – go for more compact – but not less than a 50MM objective lens. And never, never compromise on quality – like our Barska binoculars with their lifetime warranty. Ted)
(Thanks to Ed Ting for permission to serialize his article here. I think it’s mandatory reading for anyone who is considering telescope binoculars for astronomy viewing. Ted)
What Can I See?
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 3,000 stars, give or take. But when you use even modest 7×35 binoculars, that number rises to roughly 100,000 stars! (And think about the possibilities with a quality pair of 25X100’s!)
Similarly, in a light-polluted suburb you may be able to see only a couple hundred stars unaided, but binoculars will cut through the murk to show you more than you could see with your unaided eye from the top of Mount Everest.
And 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 telescope binoculars and suitably detailed sky maps and guidebooks.
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 telescope 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 telescope binoculars 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.
Make sure to read the next installments of this article! Thanks for coming by.
I went camping with my son last week. We brought a tent and were going to enjoy a couple of nights out, in the Golan Heights. Unfortunately, the tent pole got left at home. Good thing the weather here is so reliable in the summer – not a chance of a drop of rain, so we slept under the stars.
Or at least I slept. Tried to. Every 5 minutes – “Wow – Dad – did you see that one!!”. “Omigosh – that was incredible.” Yep – next time – I sleep in the tent, he gets the telescope binoculars and sleep outside, far from me.
This is the first of many posts, I hope, on Binocular telescopes. There isn’t really a good place on the web to collect all the info on the astronomy binocular, poor cousin of the telescope.
Kind of reminds me of the first days of the CD. I had a friend who had spent over $150 on his phonograph needle – I bought my first CD player (a nice Denon model) for less than that. He turned up his nose, but looked worried.
Now the situation here isn’t quite the same – large astronomy binoculars are not going to replace the telescope. But for the amateur astronomer, out to take a peek at the night skies – what could be easier than a big pair of 100’s – set up in seconds on a telescope – no problems squinting or finding the area you want to see. Simple, easy, portable. Sure – not the same detail, but still pretty serviceable.
So, that’s what we are going to discuss here. The glories of the simple way to astronomy.
Y’all come back now!
