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Lurie–Houghton Telescope
The Houghton telescope or Lurie–Houghton telescope is a catadioptric telescope. Houghton's original design was patented in 1944. Instead of the fairly hard to make Schmidt corrector plate, Schmidt and heavy meniscus corrector, meniscus (Maksutov) corrector lens (optics), lenses, the corrector for the Houghton is relatively easy to make. It consists of two lenses: a positive and a negative, set at the front of the telescope which fixes the telescope's aperture. All lens and mirror surfaces are spherical mirror, spheroidal, which eases construction. These lenses are relatively thin, though not as thin as the Schmidt corrector plate, Schmidt corrector. With a good anti-reflective coating, light loss and "ghost" reflections are minimal. Lurie slightly modified Houghton's original design by adding a diagonal mirror to direct the focused light outside the telescope tube in the same way as a Newtonian telescope. The corrector Each surface of the lenses in the correctorThe total power ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Lh Scope Front Closeup 600x430
LH or lh may refer to: Arts and entertainment *Laurel and Hardy, a comedy double act during the early Classical Hollywood era of American cinema * "Little Hide", 1998 single by Snow Patrol *Lovehammers, a Chicago-based band *''Love Hina'', a 1998 popular manga (and anime) series by author Ken Akamatsu *''The Lurking Horror'', an interactive fiction game released in 1987 Businesses and organizations *Korea Land and Housing Corporation, a South Korean state-owned housing company *LabCorp (stock symbol LH), a clinical laboratory company *Lernout & Hauspie, a former Belgium-based speech and language technology company *''Lifehacker'', a blog website owned by Gawker Media *Literary and Historical Society (University College Dublin) *Lufthansa (IATA airline designator), large European airline Places *Le Havre, a French city *Lincoln Highway, in the US *Locks Heath, a suburb of Fareham, UK *County Louth, Ireland (code LH) Science and technology * LH, a type of single-mode optical fiber ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Chromatic Aberration
In optics, chromatic aberration (CA), also called chromatic distortion and spherochromatism, is a failure of a lens to focus all colors to the same point. It is caused by dispersion: the refractive index of the lens elements varies with the wavelength of light. The refractive index of most transparent materials decreases with increasing wavelength. Since the focal length of a lens depends on the refractive index, this variation in refractive index affects focusing. Chromatic aberration manifests itself as "fringes" of color along boundaries that separate dark and bright parts of the image. Types There are two types of chromatic aberration: ''axial'' (''longitudinal''), and ''transverse'' (''lateral''). Axial aberration occurs when different wavelengths of light are focused at different distances from the lens (focus ''shift''). Longitudinal aberration is typical at long focal lengths. Transverse aberration occurs when different wavelengths are focused at different positions i ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Spider Vane
A secondary mirror (or secondary) is the second deflecting or focusing mirror element in a reflecting telescope. Light gathered by the primary mirror is directed towards a focal point typically past the location of the secondary. Secondary mirrors in the form of an optically flat ''diagonal mirror'' are used to re-direct the light path in designs such as Newtonian reflectors. They are also used to re-direct and extend the light path and modify the final image in designs such as Cassegrain reflectors. The secondary is typically suspended by X-shaped struts (sometimes called a "spider") in the path of light between the source and the primary, but can be mounted on other types of mounts or optical elements such as optical windows, or schmidt and meniscus corrector plates. Employing secondary mirrors in optical systems causes some image distortion due to the obstruction of the secondary itself, and distortion from the spider mounts, commonly seen as cross-shaped diffraction spikes r ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Diffraction Spike
Diffraction spikes are lines radiating from bright light sources, causing what is known as the starburst effect or sunstars in photographs and in vision. They are artifacts caused by light diffracting around the support vanes of the secondary mirror in reflecting telescopes, or edges of non-circular camera apertures, and around eyelashes and eyelids in the eye. Diffraction spikes due to support vanes In the vast majority of reflecting telescope designs, the secondary mirror has to be positioned at the central axis of the telescope and so has to be held by struts within the telescopes tube. No matter how fine these support rods are they diffract the incoming light from a subject star and this appears as diffraction spikes which are the Fourier transform of the support struts. The spikes represent a loss of light that could have been used to image the star. Although diffraction spikes can obscure parts of a photograph and are undesired in professional contexts, some amateur a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Vignetting
In photography and optics, vignetting is a reduction of an image's brightness or saturation toward the periphery compared to the image center. The word ''vignette'', from the same root as ''vine'', originally referred to a decorative border in a book. Later, the word came to be used for a photographic portrait that is clear at the center and fades off toward the edges. A similar effect is visible in photographs of projected images or videos off a projection screen, resulting in a so-called "hotspot" effect. Vignetting is often an unintended and undesired effect caused by camera settings or lens limitations. However, it is sometimes deliberately introduced for creative effect, such as to draw attention to the center of the frame. A photographer may deliberately choose a lens that is known to produce vignetting to obtain the effect, or it may be introduced with the use of special filters or post-processing procedures. When using superzoom lenses, vignetting may occur all alo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Foucault Test
The Foucault knife-edge test is an optical test to accurately measure the shape of concave curved mirrors. It is commonly used by amateur telescope makers for figuring primary mirrors in reflecting telescopes. It uses a relatively simple, inexpensive apparatus compared to other testing techniques. Overview The Foucault knife-edge test was described in 1858 by French physicist Léon Foucault as a way to measure conic shapes of optical mirrors. It measures mirror surface dimensions by reflecting light into a knife edge at or near the mirror's centre of curvature. In doing so, it only needs a tester which in its most basic 19th century form consists of a light bulb, a piece of tinfoil with a pinhole in it, and a razor blade to create the knife edge. The testing device is adjustable along the X-axis (knife cut direction) across the Y-axis (optical axis), and is usually equipped with measurable adjustment to 0.001 inch (25 µm) or better along lines parallel to the optical ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Lh Design Equations S
LH or lh may refer to: Arts and entertainment *Laurel and Hardy, a comedy double act during the early Classical Hollywood era of American cinema * "Little Hide", 1998 single by Snow Patrol * Lovehammers, a Chicago-based band *'' Love Hina'', a 1998 popular manga (and anime) series by author Ken Akamatsu *''The Lurking Horror'', an interactive fiction game released in 1987 Businesses and organizations * Korea Land and Housing Corporation, a South Korean state-owned housing company * LabCorp (stock symbol LH), a clinical laboratory company * Lernout & Hauspie, a former Belgium-based speech and language technology company *''Lifehacker'', a blog website owned by Gawker Media * Literary and Historical Society (University College Dublin) *Lufthansa (IATA airline designator), large European airline Places *Le Havre, a French city *Lincoln Highway, in the US *Locks Heath, a suburb of Fareham, UK *County Louth, Ireland (code LH) Science and technology * LH, a type of single-mode optical ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Interferometry
Interferometry is a technique which uses the ''interference'' of superimposed waves to extract information. Interferometry typically uses electromagnetic waves and is an important investigative technique in the fields of astronomy, fiber optics, engineering metrology, optical metrology, oceanography, seismology, spectroscopy (and its applications to chemistry), quantum mechanics, nuclear and particle physics, plasma physics, remote sensing, biomolecular interactions, surface profiling, microfluidics, mechanical stress/strain measurement, velocimetry, optometry, and making holograms. Interferometers are devices that extract information from interference. They are widely used in science and industry for the measurement of microscopic displacements, refractive index changes and surface irregularities. In the case with most interferometers, light from a single source is split into two beams that travel in different optical paths, which are then combined again to produce interfer ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Maksutov Telescope
The Maksutov (also called a "Mak") is a catadioptric telescope design that combines a spherical mirror with a weakly negative meniscus lens in a design that takes advantage of all the surfaces being nearly "spherically symmetrical". The negative lens is usually full diameter and placed at the entrance pupil of the telescope (commonly called a "corrector plate" or "meniscus corrector shell"). The design corrects the problems of off-axis aberrations such as coma found in reflecting telescopes while also correcting chromatic aberration. It was patented in 1941 by Russian optician Dmitri Dmitrievich Maksutov. Maksutov based his design on the idea behind the Schmidt camera of using the spherical errors of a negative lens to correct the opposite errors in a spherical primary mirror. The design is most commonly seen in a Cassegrain variation, with an integrated secondary, that can use all-spherical elements, thereby simplifying fabrication. Maksutov telescopes have been sold on the ama ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Coma (optics)
In optics (especially telescopes), the coma (), or comatic aberration, in an optical system refers to aberration inherent to certain optical designs or due to imperfection in the lens or other components that results in off-axis point sources such as stars appearing distorted, appearing to have a tail (coma) like a comet. Specifically, coma is defined as a variation in magnification over the entrance pupil. In refractive or diffractive optical systems, especially those imaging a wide spectral range, coma can be a function of wavelength, in which case it is a form of chromatic aberration. Overview Coma is an inherent property of telescopes using parabolic mirrors. Unlike a spherical mirror, a bundle of parallel rays parallel to the optical axis will be perfectly focused to a point (the mirror is free of spherical aberration), no matter where they strike the mirror. However, this is only true if the rays are parallel to the axis of the parabola. When the incoming rays strike the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Catadioptric
A catadioptric optical system is one where refraction and reflection are combined in an optical system, usually via lenses (dioptrics) and curved mirrors (catoptrics). Catadioptric combinations are used in focusing systems such as searchlights, headlamps, early lighthouse focusing systems, optical telescopes, microscopes, and telephoto lenses. Other optical systems that use lenses and mirrors are also referred to as "catadioptric", such as surveillance catadioptric sensors. Early catadioptric systems Catadioptric combinations have been used for many early optical systems. In the 1820s, Augustin-Jean Fresnel developed several catadioptric lighthouse reflectors. Léon Foucault developed a catadioptric microscope in 1859 to counteract aberrations of using a lens to image objects at high power. In 1876 a French engineer, A. Mangin, invented what has come to be called the Mangin mirror, a concave glass reflector with the silver surface on the rear side of the glass. The two surfaces o ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Spherical Aberration
In optics, spherical aberration (SA) is a type of optical aberration, aberration found in optical systems that have elements with spherical surfaces. Lens (optics), Lenses and curved mirrors are prime examples, because this shape is easier to manufacture. Light rays that strike a spherical surface off-centre are refraction, refracted or reflection (physics), reflected more or less than those that strike close to the centre. This deviation reduces the quality of images produced by optical systems. Overview A spherical lens has an Optical aberration#Aberration of elements, i.e. smallest objects at right angles to the axis, aplanatic point (i.e., no spherical aberration) only at a radius that equals the radius of the sphere divided by the index of refraction of the lens material. A typical value of refractive index for crown glass is 1.5 (see List of refractive indices, list), which indicates that only about 43% of the area (67% of diameter) of a spherical lens is useful. It is o ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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