télescope

A telescope is an optical instrument that uses lenses or mirrors to observe distant objects by collecting electromagnetic radiation, such as visible light. The primary purpose of a telescope is to magnify the apparent size of an object, making it appear closer and larger, and to increase its brightness, allowing fainter objects to be seen. Telescopes are fundamental tools in astronomy, enabling scientists to study celestial bodies like planets, stars, galaxies, and nebulae.

There are two main types of optical telescopes: refractors and reflectors. Refracting telescopes use lenses to focus light, while reflecting telescopes use mirrors. Refractors have an objective lens at the front that gathers light and forms an image at the focal point. Reflectors use a curved mirror, typically a parabolic mirror, to gather and focus light onto a secondary mirror or directly onto a detector. Each type has its advantages and disadvantages regarding cost, size, image quality, and maintenance.

Beyond optical telescopes, instruments designed to detect other forms of electromagnetic radiation, such as radio waves, X-rays, and gamma rays, are also commonly referred to as telescopes. These non-optical telescopes have opened up new windows into the universe, revealing phenomena invisible to the human eye. The development of more powerful and sophisticated telescopes, both ground-based and space-based, continues to drive astronomical discovery and expand our understanding of the cosmos.