Editing Refracting telescope (section)

{{Short description|Type of optical telescope}}
{{Redirect-distinguish|Keplerian telescope|Kepler space telescope}}
{{Use dmy dates|date=September 2020}}
[[File:Zeiss2.jpg|thumb|A 200 mm diameter refracting telescope at the [[Poznań Observatory]]]]

A '''refracting telescope''' (also called a '''refractor''') is a type of [[optical telescope]] that uses a [[lens (optics)|lens]] as its [[objective (optics)|objective]] to form an image (also referred to a '''[[dioptrics|dioptric]] [[telescope]]'''). The refracting telescope design was originally used in spyglasses and [[astronomy|astronomical]] telescopes but is also used for [[long-focus lens|long-focus]] [[camera lens]]es. Although large refracting telescopes were very popular in the second half of the 19th century, for most research purposes, the refracting telescope has been superseded by the [[reflecting telescope]], which allows larger [[aperture]]s. A refractor's [[magnification]] is calculated by dividing the focal length of the objective lens by that of the [[eyepiece]].<ref>{{cite web |url=http://www.northern-stars.com/tel_magnification.htm |title=Telescope Calculations |publisher=Northern Stars |access-date=2013-12-20}}</ref>

Refracting telescopes typically have a lens at the front, then a [[optical train|long tube]], then an eyepiece or instrumentation at the rear, where the telescope view comes to focus. Originally, telescopes had an objective of one element, but a century later, two and even three element lenses were made.

Refracting telescopes use technology that has often been applied to other optical devices, such as [[binoculars]] and [[zoom lens]]es/[[telephoto lens]]/[[long-focus lens]].