[en] This paper reports that an expanding telescope can produce a very low divergence particle beam, provided that the beam optics have sufficient quality in order not to introduce large aberrations. Even as late as two years ago, most beamline designs were carried out using first-order computer codes, and there existed little experimental work to describe the third-order aberrations introduced by an expanding telescope. It was installed during the summer of 1987 and tested with a 50 MeV H^- beam. The telescope consisted of a singlet eyepiece and triplet objective lens with a twenty times magnification. It performed to the design specifications of twenty-five microradians rms beam divergence with a parallel focus. The measured geometric aberrations were found to be in agreement with the computer calculations