Telescope Foundations and Spectrum-Based Types

Definition and purpose of telescopes

A telescope is an instrument used to observe distant objects by detecting electromagnetic radiation that the objects emit, absorb, or reflect. Historically, telescopes were optical devices that used lenses and/or curved mirrors to gather light and form an image. Today, the term “telescope” covers a wide range of instruments designed to detect different regions of the electromagnetic spectrum, and sometimes other kinds of detectors. The purpose of telescopes is to make faraway targets observable and measurable by collecting radiation and improving how that radiation is focused or detected. Because Earth’s atmosphere blocks most wavelengths, telescopes can be placed on the ground or in space depending on the wavelength being studied. Different telescope designs are used for different frequency bands (e.g., optical telescopes for visible light, radio telescopes for longer wavelengths, and specialized X-ray and gamma-ray instruments), allowing astronomers to study the universe across the electromagnetic spectrum.

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Etymology of the word telescope

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