Effelsberg radio telescope. Underside of the dish of the Effelsberg 100-metre radio telescope, sited near Bonn, Germany. This is used exclusively for research in radio astronomy, both as an individual instrument and as part of interferometry networks. It is one of the world's largest fully steerable antennae, and operates in a wavelength range from 90 centimetres to 3.5 millimetres. The Effelsberg radio telescope began operating in 1972. Ground- based radio astronomy is possible because Earth's atmosphere is transparent to radio waves. Galaxies and nebulae are common sources of radio waves. The streaks in the sky are star trails.