A
Spotting Scope is a portable telescope, optimized for the observation of terrestrial objects. 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
- ergonomically designed and located knob for focus control
- tethered elastomeric lens cap
- 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. All else being equal, the larger the objective, the more heavy and expensive the telescope.
There are three
types of spotting scope:
"straight-through" spotting scopes (the eyepiece is one the same axis as the body of the spotting scope),
"angled" spotting scopes (the eyepiece is at an angle of about 45 degrees to the body of the spotting scope), and, rarely, a more complex, shoulder-mounted design.
Straight-through spotting scope are easier to use from, say, inside a car, while
angled spotting 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 80X lead to poorer brightness and, even on a tripod, shake can be a problem. The field of view is also limited.
Usually for birdwatching,
20X or 40X spotting scopes are favoured. This gives a good field of view and a bright image. Amongst aircraft spotters the term "pole" is used as a shorthand expression meaning telescope. The related verb "to pole-off" therefore means reading some identication marks of an aeroplane by using a telescope. Other users might employ the same slang term.
Spotting scope manufacturers fall into several groups. At the top end of the market, it is generally accepted that three manufacturers compete strongly for the ultimate in quality:
Swarovski are the most expensive of all, closely followed by
Leica, and
Zeiss. Several manufacturers produce
spotting scopes that are generally thought to be of almost equal quality to the top three, but at about half the price, among them
Alpen,
Nikon and
Yukon.