A spotting scope is a portable telescope, optimized for the observation of objects on the ground or in trees, especially birds, deer, turkey and other game animals. The magnification of a spotting scope is typically on the order of 20X to 60X. Other common features include: somewhat "rugged" or rubber-armoured design; convenient mounting for attaching to a tripod; knob for focus control; attached lens cap; and a range of eyepieces to give different magnifications, or a variable "zoom" eyepiece to give a range of magnifications (e.g. 20-60X)
The light gathering power of a spotting scope is determined by the width of the objective lens, typically between 55 and 80 mm. Typically, the larger the objective, the more heavy and expensive the telescope.
There are three types of scope: "straight-through" (the eyepiece is on the same axis as the body of the scope), "angled" (the eyepiece is at an angle of about 45 degrees to the body of the scope), and, rarely, a more complex, shoulder-mounted design. Straight-through scopes are easier to use from inside a vehicle while angled scopes are more comfortable for tall people and more easily shared by people of different heights.
The choice of the eyepiece lens determines the overall magnification. The best magnification is decided by a number of factors. Magnifications of less than 20X are unusual, as (much cheaper and lighter) binoculars or monoculars can provide this. Magnifications of more than 60X lead to poorer brightness and, even on a tripod, shake can be a problem. The field of view is also limited.
Spotting scopes are popular when used in longrange hunting mounted on a lightweight hunting tripod. 20X or 30X are favoured for birdwatching. 20x-60x variable powers are used for longrange hunting if combined with solid mounting platforms. This gives a good field of view and a bright image.
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