An optical telescope is a telescope which is used to gather and focus light mainly from the visible part of the electromagnetic spectrum to directly view a magnified image for making a photograph, or collecting data through electronic image sensors.
There are three primary types of optical telescope: Refractors which use lenses (dioptrics), reflectors which use mirrors (catoptrics), and catadioptric telescopes which use both lenses and mirrors in combination.
A telescope's light gathering power and ability to resolve small detail is directly related to the diameter (or aperture) of its objective (the primary lens or mirror that collects and focuses the light). The larger the objective, the more light the telescope can collect and the finer detail it can resolve.
Telescopes and binocular telescopes can be used for activities such as observational astronomy, ornithology, pilotage and reconnaissance, or watching sports or performance arts.
Read more about Optical Telescope: History, Principles, Angular Resolution, Focal Length and F-ratio, Light-gathering Power, Imperfect Images, Astronomical Research Telescopes
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