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.

Stars, galaxies, quasars, and other astronomical objects emit radio waves, which can be detected with a radio telescope consisting of an antenna system and a radio receiver. In the most common kind of radio telescope, the parabolic reflector, or dish, focuses the incoming radio waves onto a small central antenna, which transmits the signal to the receiver. 

Radio astronomy and optical astronomy both examine electromagnetic radiation originating from outside the Earth's atmosphere.