Glossary term: Telescope

Description: A telescope is a device that collects photons (of light or other wavelengths) from distant objects and provides information (e.g. an image) about them to an observer. Early telescopes (from the beginning of 17th century) used lenses as optical elements (see refracting telescope). Later on this expanded to mirrors (see reflecting telescope). The largest optical telescopes are reflecting telescopes. In the 20th century, telescopes for studying other regions of electromagnetic radiation were invented, so there now exist radio telescopes, infrared telescopes, X-ray telescopes, etc. Because celestial sources are faint, astronomers tend to build large aperture telescopes to collect more light and reach finer angular resolutions.

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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".