how to... choose the right binoculars
How to pick the right pair for clear, crisp views
With Christmas around the corner, no doubt many of you will be wondering what to buy that special someone. If they are interested in astronomy the obvious gift would be a telescope, right? Wrong! They might not be ready for something as powerful and as complicated as that, especially if just starting out in the hobby. A great alternative is a pair of binoculars – they’re not so powerful that they can’t be used by an absolute beginner, and they’re cheaper and less complicated to use than a telescope too. But which pair to buy?
The good news is that it is really easy to identify a pair of binoculars that will be suitable for astronomy use; all you have to do is hold them, take a look at and through them and work out a very simple sum using the numbers printed on them.
First of all, weight is very important. If a pair of binoculars is too large and heavy for them to be held and supported by hand they will quickly become a chore to use. If you can’t support them properly everything you look at through them will shudder and shake. You can mount larger pairs of binoculars on a tripod with an adaptor, but that makes it harder to aim them at their targets. Avoid that for an absolute beginner. On the other hand, a pair of binoculars that is very small and lightweight will offer poor magnification and a very narrow field of view, so beware those too.
There’s no substitute for actually looking through a pair of binoculars, and a good retailer will have no problem with you taking your prospective purchase to their shop door and trying them out. If the image you see after focusing is still blurry, has colour fringes or is even split into two parts, that pair is no use. Look at the colours of the front lenses too. Ones that are coated orange, red or green are designed to cut down contrast – useful for daytime activities, but not for astronomy because you want as much contrast as possible.
Every pair of binoculars has two numbers on it – 7x35, 10x50, 25x50 and so on. These stand for the power of magnification and the aperture of their front lenses. To be good for astronomy the second number divided by the first should give you a value of five or higher. This figure represents how much light comes out of the binoculars and goes into your eyes. A figure of five is ideal.
Don't panicIt’s not as hard to pick a good pair of binoculars as you might think. It just takes a little time and comparison. You get what you pay forDon’t be tempted by budget or cheap binoculars. It’s well worth paying a little extra for equipment that will last. Don't be afraid to askA good retailer won’t mind you asking if you can test outside their shop if it helps you buy the right equipment. Crunch the numbersDoing a simple sum will save you buying the wrong binoculars; don’t just assume the pair you like the look of will work.Avoid shake, rattle and rollIf you feel you need to put your binoculars on a tripod, go ahead. If your hands are shaking you won’t be able to see a thing through them.