On choosing binoculars and telescopes

It is easy to feel daunted by the wide variety of choice available when looking for a pair of binoculars for birdwatching or other activities that benefit from being able to view things more closely. With prices for top of the range binoculars now nudging £1000 and for telescopes quite well over that figure, these are not insubstantial purchases for most budgets.

Your binoculars have to suit your eyes and your hands as well as your pocket. Fortunately, there are a number of simple rules to help to guide you to the right pair for you. The first, and most important, rule is to try before you buy. Many retailers offer field days at local reserves where you can try a variety of makes in something approaching real field conditions. Not all will be able to stock all makes, however, and to look at an unrivalled variety you will probably need to go the annual British Birdwatching Fair held at Rutland Water each August, or one of the smaller birdfairs held elsewhere. The location will probably have been chosen to give you good views, so, if possible, remember to try your favoured types with more tricky subjects, such as backlit birds, never, of course, looking too close to the sun. A good retailer will put no pressure on you, but will be able to offer useful advice. Reviews in magazines or on the internet will help to give you a good idea of what to expect, but are no substitute for trying them out with your own eyes.

The next thing to remember is that in general terms price is positively correlated with quality. Even if they are beyond your budget, it is worth trying one of the top price models just to see what is available. In the longer run, it may be most sensible to go for the best you can afford rather than very quickly find that you want to upgrade. There is also a trade-off over the price range: in general terms, optical quality improves faster between the lower and mid-range than it does between the mid and top range of prices, while the reverse is true of construction quality.

One decision is now more or less made for you. The traditional style of binoculars, called the "porro prism", where each barrel is stepped and the whole looks a bit like a stylised "W", has largely given way to the "roof prism" where the barrels are parallel to each other.

Binoculars are usually described by two numbers, for example, 8 x 40. The first number is the magnification and the second is the size in millimetres of the object lens (the furthest away from your eye). Letters or names after these two numbers are usually just manufacturers' banter and can be largely ignored. Dividing the object lens by the magnification will give a number which provides an indication of the binoculars' light gathering ability (the higher the number, the more light). As a general rule, it is prudent not to go much below 4. Choosing a magnification is an important decision: below 8 and you may find yourself disappointed with the size of the image, above 10 and you probably won't be able to hold them still and may find it harder to get onto close birds. Between 8 x 30 and 10 x 50 there is a wide variety of combinations to suit most requirements.

Two exceptions to the general rules should be mentioned: for "mini" binoculars, which are suited to those who have to be really concerned about weight or want a spare pair that can easily be carried in a pocket, the size of the object lens will often be only 20 or 25 millimetres and the figure obtained by division hovering below or only just over 3. For those concerned about their ability to hold the higher magnifications steady, a small number of image stabilised binoculars are available, though these do come at the cost of extra weight.

Binoculars of the same basic magnification and object lens size will still come with a lot of differences in detail, and only you can decide which suit you better. This is especially true for spectacle wearers when considering different types of eyecups. Other factors you will need to take into consideration include the field of view and how close you can focus (especially important for those who want to get good views of insects). Some prefer the focus to go from close to infinity with as little movement of the focussing wheel as possible. You will need to check that the individual eye focussing mechanism suits you: some lock, others don't. And then, there is the whole feel in your hands: some people like thumb grips on the underside, others find them a distraction. It has to be a personal choice.

The question of weight is also very important to some users and manufacturers have gone to some lengths to reduce weight with some of the most modern designs. In addition, modern straps and harnesses can spread the load, to the point where you probably do not need to let weight count against a binocular you otherwise like.

Once you know that birdwatching is for you, you will soon find that a telescope will considerably enhance your experience. The considerations for telescopes are much the same as for binoculars, especially trying before you buy, but there are some differences.

Object lens sizes are rather larger than for binoculars and for a general purpose telescope a lens of between 60 and 80 millimetres is normal, though 100 millimetres is available. Magnifications are also greater: below 20 is likely to not to be enough, but over 40 is likely to run out of light in all but good conditions. 30 magnifications is a good all-round size, but may leave those interested in distant birds on reservoirs or the sea more than spectacular close-up views of birds that are already not too distant a little short of power on occasions. Zoom lenses, often offering from 20 to 60 magnifications with the same eyepiece may provide the solution and have many fans. On any telescope, however, a zoom will always give a smaller field of view and less light than a fixed magnification eyepiece of the same power: only you can decide which is more important to your circumstances. Many telescopes offer a choice of glass: various names denote the higher quality and again only you can decide which suits you better.

You cannot escape the weight question with a telescope, because whatever the weight of the telescope you will undoubtedly need a tripod as well, in order to keep it stable. In general, the heavier the tripod, the more stable, though the lighter carbon fibre tripods do tend to offer greater stability for a lighter weight. Again, a good strap will distribute the load.

Are top of the range optics worth the price? I can only say that since upgrading some years ago to 8 x 50 binoculars (I don't notice the weight because they are superbly balanced) and an 80 millimetre high definition glass telescope with a fixed 30 magnification eyepiece and carbon fibre tripod, I just wish such equipment had been available when I first started birdwatching fifty years ago. Over that period of time the improvement has been considerable; now the rate of improvement is somewhat slower and I do not expect to upgrade again for a few years (though I could be tempted by one of the new zooms for the few occasions each year when I would welcome more power).

Whatever optics you choose, do enjoy your birdwatching!

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