A third type of optical observatory is the solar observatory. Given the sun's enormous brightness, observatories that study the star nearest to Earth must have instruments that can handle extremely intense radiation. The Robert R. McMath Solar Telescope at Kitt Peak National Observatory in Arizona focuses light from the sun down a long, slanting tunnel to an underground facility where the heavily filtered light is used to produce detailed images of the sun's rapidly changing atmosphere. To study the outer atmosphere, or corona, of the sun, a coronagraph is used to block the main light of the sun's disk, allowing the fainter corona to be observed. Antenna VLBI Radio observatories.
Radio observatories tend to be somewhat less specialized than optical observatories.
A radio telescope facility may be used for the radar mapping of planets in the solar system or for detailed studies of the distant quasars billions of light years away. Since radio waves are able to penetrate obscuring dust that absorbs light, many objects not visible in optical telescopes are easily studied by radio observatories. Computers are frequently used to process the signals received by the radio telescopes, converting them into useful images that can be studied by astronomers. Because radio waves have much longer wavelengths than light waves, radio telescopes are much bigger than their optical counterparts. The largest single radio antenna is in Arecibo, Puerto Rico.