telescopes

A telescope is an instrument that gathers electromagnetic radiation from distant objects and forms magnified images for study. While most are used for visible light, many telescopes also operate in infrared, radio, ultraviolet, and other bands. The main goals are to collect more light and to improve angular resolution, enabling detection of faint objects and fine details. The light-gathering power scales with the aperture, and resolution is set by diffraction and by atmospheric conditions on Earth.

Historically, practical optical telescopes emerged in the early 17th century. Galileo popularized their use for astronomy, and Isaac Newton developed the reflecting telescope to reduce chromatic aberration. In the 20th century, larger mirrors and advanced mounts, along with space-based observatories, greatly advanced capabilities.

Main types are refractors (lenses), reflectors (mirrors), and catadioptrics (lenses and mirrors in compact designs). A telescope comprises a primary optic, a light path to eyepieces or detectors, a tube, and a mounting system (equatorial or alt-azimuth). Aperture governs light collection and, with wavelength, affects resolution; magnification is roughly the focal-length ratio of the telescope to the eyepiece.

Observations are influenced by instrument quality and observing conditions. Refractors may suffer chromatic aberration; reflectors require alignment (collimation). Modern practice uses adaptive optics and digital imaging to counter atmospheric effects. Telescopes support visual observing, astrophotography, spectroscopy, and space science, ranging from small consumer instruments to large research observatories.