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Littrow Expansion
Littrow expansion and its counterpart Littrow compression are optical effects associated with slitless imaging spectrographs. These effects are named after Austrian physicist Otto von Littrow. In a slitless imaging spectrograph, light is focused with a conventional optical system, which includes a transmission or reflection grating as in a conventional spectrograph. This disperses the light, according to wavelength, in one direction; but no slit is interposed into the beam. For pointlike objects (such as distant stars) this results in a spectrum on the focal plane of the instrument for each imaged object. For distributed objects with emission-line spectra (such as the Sun in extreme ultraviolet), it results in an image of the object at each wavelength of interest, overlapping on the focal plane, as in a spectroheliograph. Description The Littrow expansion/compression effect is an anamorphic distortion of single-wavelength image on the focal plane of the instrument, due to a geom ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Spectrograph
An optical spectrometer (spectrophotometer, spectrograph or spectroscope) is an instrument used to measure properties of light over a specific portion of the electromagnetic spectrum, typically used in spectroscopic analysis to identify materials. The variable measured is most often the irradiance of the light but could also, for instance, be the polarization state. The independent variable is usually the wavelength of the light or a closely derived physical quantity, such as the corresponding wavenumber or the photon energy, in units of measurement such as centimeters, reciprocal centimeters, or electron volts, respectively. A spectrometer is used in spectroscopy for producing spectral lines and measuring their wavelengths and intensities. Spectrometers may operate over a wide range of non-optical wavelengths, from gamma rays and X-rays into the far infrared. If the instrument is designed to measure the spectrum on an absolute scale rather than a relative one, then it ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Austria
Austria, formally the Republic of Austria, is a landlocked country in Central Europe, lying in the Eastern Alps. It is a federation of nine Federal states of Austria, states, of which the capital Vienna is the List of largest cities in Austria, most populous city and state. Austria is bordered by Germany to the northwest, the Czech Republic to the north, Slovakia to the northeast, Hungary to the east, Slovenia and Italy to the south, and Switzerland and Liechtenstein to the west. The country occupies an area of and has Austrians, a population of around 9 million. The area of today's Austria has been inhabited since at least the Paleolithic, Paleolithic period. Around 400 BC, it was inhabited by the Celts and then annexed by the Roman Empire, Romans in the late 1st century BC. Christianization in the region began in the 4th and 5th centuries, during the late Western Roman Empire, Roman period, followed by the arrival of numerous Germanic tribes during the Migration Period. A ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Otto Von Littrow
Otto von Littrow (14 February 1843, Vienna – 7 November 1864, Vienna) was an Austrian astronomer and physicist. He is known for his contributions in spectrometer instrumentation. Son of astronomer Karl L. Littrow and women's movement leader Auguste von Littrow, grandson of astronomer Joseph Johann von Littrow, both his father and grandfather were directors of the Vienna Observatory. He studied with Hermann von Helmholtz and Gustav Kirchhoff at the Heidelberg University, and completes his doctorate degree in 1864. He was, as Constantin von Wurzbach puts it, "Destined for a scientific career by talent, birth and upbringing". He died from typhoid fever Typhoid fever, also known simply as typhoid, is a disease caused by '' Salmonella enterica'' serotype Typhi bacteria, also called ''Salmonella'' Typhi. Symptoms vary from mild to severe, and usually begin six to 30 days after exposure. Often th ... in Vienna in 1864. References 19th-century Austrian astronomers Astrono ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Extreme Ultraviolet
Extreme ultraviolet radiation (EUV or XUV) or high-energy ultraviolet radiation is electromagnetic radiation in the part of the electromagnetic spectrum spanning wavelengths shorter than the hydrogen Lyman-alpha line from 121 nm down to the X-ray band of 10 nm. By the Planck–Einstein equation the EUV photons have energies from 10.26 eV up to 124.24 eV where we enter the X-ray energies. EUV is naturally generated by the solar corona and artificially by plasma, high harmonic generation sources and synchrotron light sources. Since UVC extends to 100 nm, there is some overlap in the terms. The main uses of extreme ultraviolet radiation are photoelectron spectroscopy, solar imaging, and lithography. In air, EUV is the most highly absorbed component of the electromagnetic spectrum, requiring high vacuum for transmission. EUV generation Neutral atoms or condensed matter do not have large enough energy transitions to emit EUV radiation. Ionizatio ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Spectroheliograph
The spectroheliograph is an instrument used in astronomy which captures a photography, photographic image of the Sun at a single wavelength of light, a monochromatic image. The wavelength is usually chosen to coincide with a optical spectrum, spectral wavelength of one of the chemical elements present in the Sun. It was developed independently by George Ellery Hale and Henri-Alexandre Deslandres in the 1890s and further refined in 1932 by Robert Raynolds McMath, Robert R. McMath to take motion pictures. The instrument comprises a prism (optics), prism or diffraction, diffraction grating and a narrow slit that passes a single wavelength (a monochromator). The light is Focus (optics), focused onto a photographic medium and the slit is moved across the disk of the Sun to form a complete image. It is now possible to make a H-alpha, filter that transmits a narrow band of wavelengths which produces a similar image, but spectroheliographs remain in use. See also * Spectrohelioscope * ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sine
In mathematics, sine and cosine are trigonometric functions of an angle. The sine and cosine of an acute angle are defined in the context of a right triangle: for the specified angle, its sine is the ratio of the length of the side opposite that angle to the length of the longest side of the triangle (the hypotenuse), and the cosine is the ratio of the length of the adjacent leg to that of the hypotenuse. For an angle \theta, the sine and cosine functions are denoted as \sin(\theta) and \cos(\theta). The definitions of sine and cosine have been extended to any real value in terms of the lengths of certain line segments in a unit circle. More modern definitions express the sine and cosine as infinite series, or as the solutions of certain differential equations, allowing their extension to arbitrary positive and negative values and even to complex numbers. The sine and cosine functions are commonly used to model periodic phenomena such as sound and light waves, the posit ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Blazed Grating
A blazed grating – also called echelette grating (from French ''échelle'' = ladder) – is a special type of diffraction grating. It is optimized to achieve maximum light efficiency in a given diffraction order. For this purpose, maximum optical power is concentrated in the desired diffraction order while the residual power in the other orders (particularly the zeroth) is minimized. Since this condition can only exactly be achieved for one wavelength, it is specified for which ''blaze wavelength'' the grating is optimized (or ''blazed''). The direction in which maximum efficiency is achieved is called the ''blaze angle'' and is the third crucial characteristic of a blazed grating directly depending on blaze wavelength and diffraction order. Blaze angle Like every optical grating, a blazed grating has a constant line spacing d, determining the magnitude of the wavelength splitting caused by the grating. The grating lines possess a triangular, sawtooth-shaped cross sect ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
