[kayaeb]

Not sure why you're being downvoted.

This is correct to an extent, the surface of a mirror needs to be polished to a degree such that abnormalities in the lens are small relative to the wavelength being observed (I think it's the diffraction limit equation, not positive atm). Radio telescopes (with cm wavelengths) require much less precision than optical ones (with sub-micron wavelengths). This telescope, FAST, actually is made out of a collection of triangular (I think) sheets arranged into a kind of dome, if it were observing optical it would act like a disco-ball instead of a parabolic mirror. Arecibo is literally a hole in the ground with rocks and crap on the reflector.

This thing actually had "first light" observations with several holes in it from triangular sections that were fritzing just kind of fluttering in the breeze. The first radio telescopes were literally built out of post-coldwar trash just kind of rigged up in the back-yard. There's a major array going in in south Africa where the antennas are like christmas tree wires that are just kind of hammered into the ground, one of the PIs showed video at a colloquium I attended of his 10 year old kids setting them up. If anything in modern science can be called "low specification" it's radio telescopes.