Glossary term: Refracting Telescope

Description: A refracting telescope is a telescope that uses a lens as its main light-gathering element. This is opposed to a reflecting telescope, which uses a mirror in this role. Refracting telescopes are still common as amateur telescopes, where a special combination of lenses that correct for unwanted color effects ("achromatic telescopes") can produce excellent image quality for visual observing and for astrophotography. In professional astronomy, refracting telescopes were largely displaced by mirror telescopes from the early 1900s onwards. Astronomers wanted ever-larger apertures (lens or mirror diameters), and it is difficult to make refracting telescopes beyond lens sizes of about one meter as a lens is only supported at the rim, leading to the heavy center of the lens sagging under gravity, distorting the lens's shape and optical properties.

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The OAE Multilingual Glossary is a project of the IAU Office of Astronomy for Education (OAE) in collaboration with the IAU Office of Astronomy Outreach (OAO). The terms and definitions were chosen, written and reviewed by a collective effort from the OAE, the OAE Centers and Nodes, the OAE National Astronomy Education Coordinators (NAECs) and other volunteers. You can find a full list of credits here. All glossary terms and their definitions are released under a Creative Commons CC BY-4.0 license and should be credited to "IAU OAE".