An optical telescope gathers and focuses light mainly from the visible part of the Electromagnetic spectrum (although some work in the infrared and ultraviolet). Optical telescopes increase the apparent angular size of distant objects, as well as their apparent bright. A radio telescope uses a large metal dish or wire mesh, usually parabolic-shaped, to reflect the radio waves to an antenna above the dish.tness.

Radio astronomy and optical astronomy both examine electromagnetic radiation originating from outside the Earth's atmosphere.A telescope is an instrument designed for the observation of remote objects by the collection of electromagnetic radiation. The first known practically functioning telescopes were invented in the Netherlands at the beginning of the 17th century. "Telescopes" can refer to a whole range of instruments operating in most regions of the electromagnetic spectrum.

Refractors were the earliest type of optical telescope. The first practical refracting telescopes appeared in the Netherlands in about 1608, and were credited to three individuals, Hans Lippershey and Zacharias Janssen, spectacle-makers in Middelburg, and Jacob Metius of Alkmaar also known as Jacob Adriaanszoon. The original design Galileo came up with in 1608 is commonly called a Galilean telescope. It uses a convex objective lens and a concave eyepiece lens.
Galileo’s best telescope magnified objects about 30 times. Because of flaws in its design, such as the shape of the lens, the images were blurry and distorted. Despite these flaws, the telescope was still good enough for Galileo to explore the sky.