Spotting scopes are small telescopes that have been modified for use by day. A spotting scope differs from an astronomical telescope in several important ways. First, a spotting scope always produces an upright image whereas a telescope may produce a reversed image or even an upside-down image (not a problem for astronomy). Second, a spotting scope is much smaller in size than a telescope, mainly for the sake of portability. Third, a spotting scope is a lower magnification instrument than a telescope, since the atmosphere by day does not allow the high magnifications used in astronomy. Fourth, a spotting scope is mounted on an ordinary photo tripod, but a telescope for astronomy requires a particular mount, often this just isnt practical for daytime use. Lastly, many, if not most, spotting scopes are waterproof and fog proof a rare feature in an astronomical telescope.
Spotting scopes are used anytime you need more magnification than a binocular provides. Spotting scopes are widely used for birding, surveillance, hunting, and viewing the landscape, wildlife, ships and other distant objects. Spotting scopes are also used for scoring targets on rifle, pistol and archery ranges, and they can also be used to some astronomy. Last, but not least, spotting scopes are also used to take long-distance pictures with a variety of cameras.
Most spotting scopes are labelled with three numbers. The first two represent the magnification, and the last number is the size of the front lens.