The design of high-magnification afocal telescopes that operate simultaneously over very-broad portions of the visible and infrared spectrums presents a significant challenge to the lens designer. Such telescopes are often used with some type of scanning sensor that requires the pupil of the telescope to be located external to the telescope to afford alignment with the sensor's pupil. The afocal telescope described in this paper comprises a single primary mirror and two lenses to form the secondary optics where each lens is made from the same material. The secondary spectrum of the telescope is maintained at a very- low level by arranging the lenses in a Schupmann dialyte form. The telescope can be corrected for axial color and Petzval, and exhibits low residual secondary spectrum by using the presented first-order design equations. In this paper, the design equations are developed, a practical design procedure is presented, and the optical performance of an example telescope is discussed.