An optical telescope focuses and concentrates visible light; radio telescopes focus and concentrate electromagnetic radiation (which means, "light") in the radio part of the spectrum.
Radio telescopes collect radio waves. Optical telescopes capture visible light waves.
The Hubble Space Telescope has a number of instruments, but the primary one is an optical telescope.
"Optical", in this case, simply means that they work with light.
They are optical telescopes.
optical
Reflector.
Different telescopes utilize different parts of the electromagnetic spectrum. Two types of optical telescope are refracting and reflecting. There are also different kinds of radio telescope investigating different bandwidths from the infra red to the untra violet
See things that don't shine in the visible spectrum.
There are telescopes used to detect radio waves and others to detect infrared radiation.
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The surface of a radio telescope doesn't have to be as flawless as the surface of an optical telescope because the radio telescope is collecting radio waves, something that will not be affected by faults in the glass. Optical telescopes, on the other hand, are collecting light, where faults in the surface can interfere with the image.