250px, Schiefspiegler telescope arrangement in which tilt effects compensate for the lateral decenter. The Schiefspiegler (lit. ''oblique mirror'' in German), also called tilted-component telescopes (TCT) and off-axis reflecting telescopes, are a type of

reflecting telescope A reflecting telescope (also called a reflector) is a telescope that uses a single or a combination of curved mirrors that reflect light and form an image. The reflecting telescope was invented in the 17th century by Isaac Newton as an alternati ...

featuring an off-axis secondary mirror, and therefore an obstruction-free light path. This is accomplished by tilting the primary mirror so that the secondary mirror does not block incoming light.

William Herschel Frederick William Herschel (; german: Friedrich Wilhelm Herschel; 15 November 1738 – 25 August 1822) was a German-born British astronomer and composer. He frequently collaborated with his younger sister and fellow astronomer Caroline H ...

was one of the first to have tilted the mirror of his telescope in order to avoid light loss due to the low reflectivity of his speculum-metal mirror. The obstructions in telescope tubes, such as secondary mirrors and their mechanical supports, cut off the intensity of captured light and cause diffraction. The diffraction causes artifacts such as the radial spikes that project from images of bright stars, and it also reduces the contrast of fine details. Schiefspieglers offer a significant increase in contrast, which is useful, for instance, for lunar and planetary study.Texereau, J. (1957). How to make a telescope (p. 400). New York: Interscience. Tilting the mirrors causes severe

coma A coma is a deep state of prolonged unconsciousness in which a person cannot be awakened, fails to respond normally to painful stimuli, light, or sound, lacks a normal wake-sleep cycle and does not initiate voluntary actions. Coma patients exhi ...

and

astigmatism Astigmatism is a type of refractive error due to rotational asymmetry in the eye's refractive power. This results in distorted or blurred vision at any distance. Other symptoms can include eyestrain, headaches, and trouble driving at nig ...

, however as

Anton Kutter Anton Kutter (13 June 1903, in Biberach an der Riß – 1 February 1985, in Biberach) was a German film director and screenwriter. He studied mechanical engineering at Stuttgart Technical University. In 1926 Kutter went to Cologne and joined ...

showed in the 1950s, by a suitable choice of radii these aberrations can be corrected to an acceptable level. The 1.6-meter New Solar Telescope at the

Big Bear Solar Observatory Big Bear Solar Observatory (BBSO) is a university-based solar observatory in the United States. It is operated by New Jersey Institute of Technology (NJIT). BBSO has a clear aperture Goode Solar Telescope (GST), which has no obscuration in the ...

, and the 4-meter

Daniel K. Inouye Solar Telescope The Daniel K. Inouye Solar Telescope (DKIST) is a scientific facility for studies of the sun at Haleakala Observatory on the Hawaiian island of Maui. Known as the Advanced Technology Solar Telescope (ATST) until 2013, it was named after Daniel K. ...

feature off-axis designs for sensitive observations of the

Sun The Sun is the star at the center of the Solar System. It is a nearly perfect ball of hot plasma, heated to incandescence by nuclear fusion reactions in its core. The Sun radiates this energy mainly as light, ultraviolet, and infrared radi ...

References

External links

Schiefspiegler Telescopes
(SEDS) Telescopes Telescope types Astronomical imaging {{optics-stub