An aplanatic total reflection telescope for use in the soft x-ray region has been constructed and tested in this laboratory. The telescope has a collecting area of 2 cm<sup>2</sup>, an angular resolution of 1 min of arc, and a field of view of 40 min of arc. The focal length is 64 cm. The grazing angle of incidence on the telescope surface is about 1° for paraxial radiation. This results in an efficiency of reflection of 0.2% in the 8–12 Å region and 5.0% at 44 Å. These characteristics make it particularly suited to the study of celestial x-ray sources from rocket- and satellite-borne instrumentation.
R. GIACCONI, N. F. HARMON, R. F. LACEY, and Z. SZILAGYI, "Aplanatic Telescope for Soft X Rays," J. Opt. Soc. Am. 55, 345-347 (1965)