The basic principle of a telescope

A telescope is a visual optical instrument used for observing distant objects. It can magnify the very small Angle of view of distant objects by a certain magnification, making them have a larger Angle of view in the image space, thus making objects that were originally impossible to see or distinguish with the naked eye clear and distinguishable. Therefore, telescopes are indispensable tools in astronomy and ground-based observations. It is an optical system that keeps the incident parallel light beam parallel when it exits through the objective lens and eyepiece. According to the principle of telescopes, they are generally classified into three types. An instrument that observes the electromagnetic radiation of distant objects by collecting electromagnetic waves is 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 has further extended to the fields of gravitational waves, cosmic rays and dark matter.

Optical telescopes in daily life are also known as "thousand-mile mirrors". It mainly includes amateur astronomical telescopes, viewing telescopes and military binoculars. The commonly used binoculars also need to add a prism system for the purpose of reducing volume and reversing the inverted image. According to the different shapes of the prism system, it can be divided into the RoofPrism system (also known as Schmidt). The principles and applications of the Biehan Roof Prism system and the PorroPrism system (also known as the Porro prism system) are similar. For personal use, small handheld telescopes should not have overly high magnification. Generally, 3 to 12 times is appropriate. When the magnification is too high, the clarity of the image will deteriorate and the shaking will be severe. Telescopes with magnification exceeding 12 times are usually fixed by means of tripods or other methods.