Any of a series of designs for grazing-incidence telescopes by the German physicist Hans Karl Herman Wolter (1911–78). To obtain a true image over an extended field of view requires photons to undergo two successive reflections from combinations of paraboloid–hyperboloid or paraboloid–ellipsoid surfaces. For imaging the commonly used design is the Wolter I telescope; for spectroscopy, where a smaller field of view but very high spatial resolution is required, the Wolter II design is appropriate.