Wolter telescope

A Wolter telescope is a telescope for X-rays using only grazing incidence optics. Visible light telescopes are built with lenses or parabolic mirrors. Neither works well for X-rays. Lenses for visible light are made of a transparent material with an index of refraction substantially different from 1, but there is no equivalent material for x-rays. Conventional mirror telescopes work poorly in the X-rays as well, since the light hits the mirrors at near-normal incidence, where the X-rays are transmitted or absorbed, not reflected.

X-rays mirrors can be built, but only if the angle of incidence is very low (typically 10 arc-minutes to 2 degrees) [cite web |url=http://www.iisc.ernet.in/academy/resonance/June2005/pdf/June2005p15-23.pdf |author=Kulinder Pal Singh |title=Techniques in X-ray Astronomy ] . These are called "glancing incidence mirrors". In 1952, Hans Wolter outlined 3 ways a telescope could be built using only this kind of mirror. [cite journal |title=Glancing Incidence Mirror Systems as Imaging Optics for X-rays |author=Wolter, H. |journal=Ann. Physik |volume=10 |pages=94 |year=1952] [cite journal |title=A Generalized Schwarschild Mirror Systems For Use at Glancing Incidence for X-ray Imaging |author=Wolter, H. |journal=Ann. Physik |volume=10 |pages=286 |year=1952] . Not surprisingly, these are called Wolter telescopes of type I, II, and III. Each has different advantages and disadvantages. [cite web |author=Rob Petre |url=http://imagine.gsfc.nasa.gov/docs/science/how_l2/xtelescopes_systems.html |title=X-ray Imaging Systems |publisher=NASA]

References

See also

*Chandra X-ray Observatory Orbiting observatory using a Wolter X-ray telescope.
*XMM-Newton Orbiting X-ray observatory using a Wolter X-ray telescope.
*Swift Gamma-Ray Burst Mission Contains a Wolter Type-I X-ray telescope