I have been reading an article that refers to telescopes but I don’t really understand telescope sizes; http://www.eso.org/public/news/eso0226/ For instance take the 3.5-m New Technology Telescope. I assume that the 3.5m refers to the diameter of the parabolic mirror. Does the 3.5m give any indication of the range of wavelengths that can be received? There is also the 10m Keck telescope. Presumably this can detect much fainter objects than the 3.5m but once again does the size of the mirror give more information than the cross sectional area of photons it can make use of? Both the above telescopes were used to examine the centre of our galaxy. They received both radio and x-ray emmissions. But radio emmissions are long wavelength and x-ray are very short wavelength. Can the above telescopes really cope with such a range of wavelengths?