Description: An optical telescope is an instrument that is used to observe and study astronomical objects in visible (optical) light. Optical telescopes use mirrors (a reflecting telescope) and/or lenses (a refracting telescope) to collect and focus light. Telescopes were originally developed to observe distant objects on Earth but were soon turned to astronomical use. Telescopes can range in size from a few centimeters across to diameters of over ten meters.

Related Terms:

• Electromagnetic Radiation
• Reflecting Telescope
• Refracting Telescope
• Telescope
• Visible Spectrum
• Lens
• Mirror

Term and definition status: This term and its definition have been approved by a research astronomer and a teacher

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".