What advantages does a radio telescope have over an optical telescope?

Answer 1

On a radio telescope the dish does not ave to be as perfect as a mirror on an optical telescope so on a radio telescope the dish can have imperfections as ong as they are no more than 1/20 of the wavelenth being detected. A wire mesh can be used instead of a mirror, which is cheaper.

Since the wavelength of radio waves is much larger than the wavelength of visible light, the resolving power of a radio telescope is higher.

Answer 2

Radio telescopes "see" in the radio portion of the electromagnetic spectrum, so they see lots of things that optical telescopes can not.

Optical telescopes have the same advantage; they see a portion of the spectrum that radio telescopes do not.