Spotting scopes are used when more magnification is needed or wanted than binoculars provide and are used widely for birding, viewing wildlife and landscapes and other objects at a great distance. Much of the terminology and technical specifications specific to spotting scopes are similar to binoculars. For example, a 20-60×82 spotting scope has a zoom magnification range of 20-60x (20 to 60 times larger than the size of an image as would be seen by the naked eye) with a front lens diameter of 82mm.
The significant increased magnification can take you well beyond the capabilities of conventional binoculars. That said, two factors, the atmosphere and the optical system of the spotting scope, should be kept in mind. Heavy air, dust, humidity, glare and wind and air currents during the day can all reduce image quality and the greater the magnification, the more drastic the reduction in image quality will be. Few locations allow you to use more than 60-80x during the day, so most spotting scopes stop at 60x. The optical system of a spotting scope will impact magnification also. As magnification is increased, some decrease in image quality will result, no matter the model. In this key area, as the old saying goes…you get what you pay for. So yes, if you want a scope that is as clear and sharp at 60x magnification as it is at 20x, then expect to pay more. Keep in mind though that most spotting scopes are used at lower magnifications, usually around 30x-40x. This is more than enough for most applications and all but the least expensive and cheapest model will produce reasonable images in this magnification range.
Assuming that you are comparing two models of similar quality, the larger the objective lens, the more detail you can see and the better image quality your scope will deliver, especially at higher magnifications. However, a large lens of mediocre quality, no matter how large, will never equal the performance of a smaller, quality lens. If you aren’t sure, opt for quality, not size.
Although not an absolute necessity, a close focus of 20 ft or less can be useful, especially if you plan to use a spotting scope with a camera.
As with binoculars, this is the distance your eye can be from the eyepiece and still see the entire field of view. As a general rule, you will need at least 14mm of eye relief to see the entire field of view with eyeglasses and people with thick glass lenses in their eyeglasses will probably need more.
While not a necessity, a waterproof scope is terrific to have. The seals in a waterproof model also prevent the infiltration of dust and dirt and therefore add to the lifespan of the spotting scope.
Due to its high magnification, hand holding a spotting scope and expecting to maintain a clear, non-blurry image is virtually impossible and therefore requires that it be supported to keep it steady. The best tripod for spotting scope you may be able to sneak by at lower magnifications with a monopod or shoulder stock, but above 40x, you must use a tripod. And the larger and heavier the scope, the larger and heavier the tripod should be. As all spotting scopes are threaded in the same fashion as a camera and therefore should fit on any standard camera or video tripod, unless you prefer, you will not need to purchase a special tripod for your spotting scope.
Best Spotting Scopes for Birding
Most agree that the best magnification range for birding with a spotting scope is 20-40x. Much higher than 40x and the field of view is too narrow to be practical, with the added drawback of a dimmer image. Keep in mind that problems such as heat waves will increase at higher magnifications. If you do a lot of dawn or twilight bird observation, or if your area is often overcast and dim, a wider objective lens will give you a better image. So you will want to choose a lens of 77-82mm. However, a larger objective lens also translates to increased size and weight. Birders who are out mostly during the day and don’t relish the thought of carrying a heavier instrument will want to consider an objective lens size of 60-65mm.
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