The telescope is a visual optical instrument used to observe distant objects, which can magnify the small opening angle of distant objects according to a certain magnification, so that it has a large opening angle in the image space, so that the objects that could not be seen or distinguished with the naked eye become clear and distinguishable. Therefore, telescopes are indispensable tools in astronomy and ground-based observation. It is an optical system that uses an objective lens and eyepieces to keep the incident parallel beam still emitted in parallel. According to the principle of telescopes, it is generally divided into three types. An instrument that collects electromagnetic waves to observe the electromagnetic radiation of distant objects, called a radio telescope, in daily life, telescopes mainly refer to optical telescopes, but in modern astronomy, astronomical telescopes include radio telescopes, infrared telescopes, X-ray and gamma ray telescopes. The concept of astronomical telescopes extends further to gravitational waves, cosmic rays, and dark matter.
Optical telescopes in daily life are also known as "clairvoyant mirrors". It mainly includes amateur astronomical telescopes, theater telescopes and military binoculars.
Commonly used binoculars also need to add a prism system for the purpose of reducing the volume and flipping the inverted image, and the prism system can be divided into the Roof Prism system (that is, the Smit-Beehan Roof Ridge Prism System) and the Paul Prism System (Porro Prism) (also known as the Pro-Prism System) according to the shape of the formula, and the principles and applications of the two systems are similar.
Small handheld telescopes for personal use should not use too large magnification, generally 3~12 times is appropriate, when the magnification is too large, the imaging clarity will become poor, and the jitter is serious, more than 12 times the telescope generally uses tripods and other ways to fix.