The University of Illinois radio telescope

The University of Illinois radio telescope is a reflector in the shape of a parabolic cylinder whose aperture is
400 feet \times 600
feet. A 425-foot-long phase-adjustable array of receiving antennas lies along the focal line and produces a pencil beam one-third degree in width, steerable in the meridian plane up to 30 degrees in either direction from the zenith. The array was designed by means of a novel procedure using both variable spacing and variable excitation to produce a prescribed beamwidth. The reflector is built of earth, utilizing a natural ravine. The purpose of the instrument is to compile a catalog of faint extragalactic radio sources.