There are basically two types of optical equipment used for bird watching: binoculars and spotting scopes.
Binoculars are one of the birdwatcher's essential tools. While it is possible to watch birds without them, the close-up views you can get with them can be breathtaking!
Most bird watching magazines carry advertisements for binoculars and other equipment and often have regular reviews too.
Remember to try the binoculars or spotting scopes for yourself before you buy them, because only you know what is best for your hands and eyes.
Most, if not all, binoculars have the same main features, such as eyepieces, central focussing wheel, dioptre adjustment and objective lenses. In addition, most have two numbers and usually a few letters marked on them, for example: 8x40W BGA.
| 8x40W BGA Explained | |
| 8x | Magnification |
| 40 | Objective lens diameter (mm) |
| W | Wide-angle |
| B | Long eye-relief |
| GA | Rubber or polyurethane armour |
The first number is the magnification. In our example the magnification is 8x, which means that whatever you look at through the binoculars will seem to be eight times larger or eight times closer than if you looked at the object with just your eyes.
The second number is the diameter of the objective lens. In our example, the diameter of the objective lens is 40 mm. The larger the objective lens, the more light can enter the binoculars and the brighter the image, but the binoculars will also be bigger and heavier.
Different manufacturers often use a variety of letters to indicate various features. However, the common ones are quite standard:
Some other recent letters: AG (silver coated), PC (phase correction), HG (high-grade), P* (Zeiss phase coating), and T* (Zeiss multi-coating) provide information about special coatings used to improve the colour and clarity of the image.
Most people do not have two eyes the same - one is usually "weaker" than the other - and so it is important that this difference is accommodated by the binoculars. Binoculars should have an individual eye (or dioptre) adjustment, often on one of the eyepieces, but sometimes part of the main central focussing mechanism.
Do not be tempted to simply buy the binoculars with the largest magnification and objective lens, such as 20x50, because these will be very heavy and difficult to hold still. The most common magnifications are 7x and 8x and these are great for most types of bird watching, especially in woodlands where you are often trying to follow moving birds, but if you plan to do a lot of bird watching at lakes and estuaries where birds are often further away then 10x are better.
As a rule of thumb, the objective lens should be about 4-5 times the magnification; this provides a good compromise between the amount of light entering your eye and the weight of the binoculars (objective lens diameter); typically, therefore, 7x32, 8x40, 10x42 or 10x50.
There are basically three main types of binoculars.
The porro prism type is the classic binocular shape with the eyepieces closer together than the larger objective lenses.
There is vast range of manufacturers offering a huge selection of sizes and features.
Roof prism binoculars tend to be more compact than porro prism and have better light-gathering properties.
Compact or miniature binoculars tend to be either small roof prism binoculars or "reverse porro prism" ones, which have the objective
lenses closer together than the eyepieces. Both types are handy for putting in your coat pocket when you do not plan on
bird watching, but don't want to be caught without!
All scopes have the same main features, an eyepiece, objective lens and focussing wheel.
How the eyepiece fits to the scope body gives rise to their description as either straight scopes or angled scopes (see photograph below). The straight eyepiece variety are common and often easier to use because the eyepiece is in line with the body of the scope and pointing in the direction that you are looking. Straight scopes are best suited to observing birds that are at or below eye level. The angled eyepieces are fitted at 45° to the body, and if the body is rotated it can become disorientating, though with practice this becomes less of a problem. Angled scopes are best suited to observing birds that are high up, for example in trees or in flight. If you are going to use a tripod, then the tripod will be lower and more stable with an angled scope (because you are looking downwards in to the eyepiece) than with a straight scope.
The size of the objective lens influences the clarity of the image. The bigger the lens, the more light is gathered and the better the image, but also the heavier and bulkier the scope which are important considerations on field trips. Common objective lens diameters include 50 mm, 60 mm, 66 mm, 77 mm, 80 mm and 85 mm.
The eyepiece sets the magnification. As with binoculars, a high magnification is not necessarily the best, because high magnification decreases the field of view, which makes targeting more difficult, decreases image brightness, decreases steadiness, and heat haze can become a problem. Common magnifications are 25x to 32x.
Also remember that the cost of the scope usually reflects build quality, optical quality, but also the manufacturer's name and reputation.
To protect the objective lens from dust and scratches, many people fit a UV haze filter.
