Many imaging X-ray telescopes consist of nested, co-axial, parabolic or hyperbolic shells. X-rays cannot reflect from silvered or aluminized surfaces. They get absorbed instantly. So, by using nested curved surfaces, the X-rays strike the surface at a shallow angle, travel inward into the nested shells and are 'skipped' several times more before they arrive at the central collector or imager where they are counted. The shape of the hyperbolic surface has to be tailored to the energy of the X-rays you want to collect, because low energy X-rays can be skipped at a less-acute angle than the high energy ones.