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Carey Mask
A Carey mask (named after the inventor, George F. Carey) is a focusing aid for astronomical telescopes. The mask is in the form of a thin card or sheet that is placed over the front aperture of the telescope. There are four series of slits in the mask which form a diffraction pattern in the image plane. In this example the two sets of slits on the left are angled at 12 degrees to each other. Those on the right are angled at 10 degrees to each other. Different telescope and imaging combinations may require slightly different angles. The diffraction pattern caused by the left hand slits will be in the form of an 'X'. The right hand slits will also form an 'X' shape, but the lines forming the 'X' will cross at a narrower angle. When perfect focus is achieved the two 'X's will be superimposed and be perfectly symmetrical. Any slight error in focus will cause the 'X's to be offset, and this is very noticeable to the naked eye. In the example images below, focus error is obvious i ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Carey Mask1
Carey may refer to: Names * Carey (given name), a given name * Carey (surname), a surname ** List of people with surname Carey Places Canada * Carey Group, British Columbia; in the Pacific * Carey Island (Nunavut) in James Bay United Kingdom * Carey, Herefordshire (see List of places in Herefordshire) * Carey Baptist Church, an independent Evangelical church in Reading, England United States * Carey, Alabama (see List of places in Alabama: A–C) * Carey, California * Carey, Georgia * Carey, Idaho * Carey, Ohio * Carey, Texas * Carey, Wisconsin * Carey, Wyoming, a locale near the eastern end of Wyoming Highway 95 * Carey Block, historic building in Wyoming * Carey Farm Site, a prehistoric archaeological site in Delaware * Carey Formation, a geologic formation in Oklahoma * Carey House (other), several * Carey Lake, a lake in Cottonwood County, in the U.S. state of Minnesota Elsewhere * Carey Glacier, Antarctica * Carey Gully, South Australia * Carey Islands, an island ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
George F
George may refer to: People * George (given name) * George (surname) * George (singer), American-Canadian singer George Nozuka, known by the mononym George * George Washington, First President of the United States * George W. Bush, 43rd President of the United States * George H. W. Bush, 41st President of the United States * George V, King of Great Britain, Ireland, the British Dominions and Emperor of India from 1910-1936 * George VI, King of Great Britain, Ireland, the British Dominions and Emperor of India from 1936-1952 * Prince George of Wales * George Papagheorghe also known as Jorge / GEØRGE * George, stage name of Giorgio Moroder * George Harrison, an English musician and singer-songwriter Places South Africa * George, Western Cape ** George Airport United States * George, Iowa * George, Missouri * George, Washington * George County, Mississippi * George Air Force Base, a former U.S. Air Force base located in California Characters * George (Peppa Pig), a 2-year-old pig ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Focusing Screen
A focusing screen is a flat translucent material, either a ground glass or Fresnel lens, found in a system camera that allows the user of the camera to preview the framed image in a viewfinder. Often, focusing screens are available in variants with different etched markings for various purposes. For instance, "overall matte" focusing screens with no etchings are a popular choice for astrophotography and other low-light situations. Overview The history of the focusing screen is almost as long as the history of the camera. Some primitive cameras consisted of a box with a board holding the lens in the front and a focusing screen in the back that was replaced by the imaging medium (plate, film holder) before taking the picture. The most common type of focusing screen in non-autofocus 35 mm SLR cameras is the split screen and microprism ring variation that aids focusing and became standard in the 1980s. The microprism ring breaks up the image unless the lens setting is in focu ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Telescopes
A telescope is a device used to observe distant objects by their emission, absorption, or reflection of electromagnetic radiation. Originally meaning only an optical instrument using lenses, curved mirrors, or a combination of both to observe distant objects, the word ''telescope'' now refers to a wide range of instruments capable of detecting different regions of the electromagnetic spectrum, and in some cases other types of detectors. The first known practical telescopes were refracting telescopes with glass lenses and were invented in the Netherlands at the beginning of the 17th century. They were used for both terrestrial applications and astronomy. The reflecting telescope, which uses mirrors to collect and focus light, was invented within a few decades of the first refracting telescope. In the 20th century, many new types of telescopes were invented, including radio telescopes in the 1930s and infrared telescopes in the 1960s. Etymology The word ''telescope'' was coine ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Aperture
In optics, an aperture is a hole or an opening through which light travels. More specifically, the aperture and focal length of an optical system determine the cone angle of a bundle of rays that come to a focus in the image plane. An optical system typically has many openings or structures that limit the ray bundles (ray bundles are also known as ''pencils'' of light). These structures may be the edge of a lens or mirror, or a ring or other fixture that holds an optical element in place, or may be a special element such as a diaphragm placed in the optical path to limit the light admitted by the system. In general, these structures are called stops, and the aperture stop is the stop that primarily determines the ray cone angle and brightness at the image point. In some contexts, especially in photography and astronomy, ''aperture'' refers to the diameter of the aperture stop rather than the physical stop or the opening itself. For example, in a telescope, the aperture ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Diffraction
Diffraction is defined as the interference or bending of waves around the corners of an obstacle or through an aperture into the region of geometrical shadow of the obstacle/aperture. The diffracting object or aperture effectively becomes a secondary source of the propagating wave. Italian scientist Francesco Maria Grimaldi coined the word ''diffraction'' and was the first to record accurate observations of the phenomenon in 1660. In classical physics, the diffraction phenomenon is described by the Huygens–Fresnel principle that treats each point in a propagating wavefront as a collection of individual spherical wavelets. The characteristic bending pattern is most pronounced when a wave from a coherent source (such as a laser) encounters a slit/aperture that is comparable in size to its wavelength, as shown in the inserted image. This is due to the addition, or interference, of different points on the wavefront (or, equivalently, each wavelet) that travel by paths of d ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Focussing
Focusing may refer to: * Adjusting an optical system to minimize defocus aberration * Focusing (psychotherapy) Focusing is an internally oriented psychotherapeutic process developed by psychotherapist Eugene Gendlin. It can be used in any kind of therapeutic situation, including peer-to-peer sessions. It involves holding a specific kind of open, non-judging ..., a psychotherapeutic technique See also * Focus (other) {{dab ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Focussing Neg
Focusing may refer to: * Adjusting an optical system to minimize defocus aberration * Focusing (psychotherapy) Focusing is an internally oriented psychotherapeutic process developed by psychotherapist Eugene Gendlin. It can be used in any kind of therapeutic situation, including peer-to-peer sessions. It involves holding a specific kind of open, non-judging ..., a psychotherapeutic technique See also * Focus (other) {{dab ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Orientation (geometry)
In geometry, the orientation, angular position, attitude, bearing, or direction of an object such as a line, plane or rigid body is part of the description of how it is placed in the space it occupies. More specifically, it refers to the imaginary rotation that is needed to move the object from a reference placement to its current placement. A rotation may not be enough to reach the current placement. It may be necessary to add an imaginary translation, called the object's location (or position, or linear position). The location and orientation together fully describe how the object is placed in space. The above-mentioned imaginary rotation and translation may be thought to occur in any order, as the orientation of an object does not change when it translates, and its location does not change when it rotates. Euler's rotation theorem shows that in three dimensions any orientation can be reached with a single rotation around a fixed axis. This gives one common way of representing ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Detail Of Focus
Detail(s) or The Detail(s) may refer to: Film and television * ''Details'' (film), a 2003 Swedish film * ''The Details'' (film), a 2011 American film * ''The Detail'', a Canadian television series * "The Detail" (''The Wire''), a television episode Music * ''Details'' (album), by Frou Frou, 2002 * Detail (record producer), Noel Fisher (born c. 1978), American music producer and performer * The Details, a Canadian rock band Periodicals * ''DETAIL'' (professional journal), an architecture and construction journal * ''Details'' (magazine), an American men's magazine See also * Auto detailing, a car-cleaning process * Level of detail (computer graphics), a 3D computer graphics concept * Security detail, a team assigned to protect an individual or group * Detaille Island Detaille Island is a small island off the northern end of the Arrowsmith Peninsula in Graham Land, Antarctica. From 1956 to 1959 it was home to "Base W" of the British Antarctic Survey and closed after ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Astrophotography
Astrophotography, also known as astronomical imaging, is the photography or imaging of astronomical objects, celestial events, or areas of the night sky. The first photograph of an astronomical object (the Moon) was taken in 1840, but it was not until the late 19th century that advances in technology allowed for detailed stellar photography. Besides being able to record the details of extended objects such as the Moon, Sun, and planets, modern astrophotography has the ability to image objects invisible to the human eye such as dim stars, nebulae, and galaxies. This is done by long time exposure since both film and digital cameras can accumulate and sum photons over these long periods of time. Photography using extended exposure-times revolutionized the field of professional astronomical research, recording hundreds of thousands of new stars, and nebulae invisible to the human eye. Specialized and ever-larger optical telescopes were constructed as essentially big cameras to rec ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bahtinov Mask
The Bahtinov mask is a device used to focus small astronomical telescopes accurately. Although masks have long been used as focusing aids, the distinctive pattern was invented by Russian amateur astrophotographer Pavel Bahtinov (russian: Павел Бахтинов) in 2005. Precise focusing of telescopes and astrographs is critical to performing astrophotography. The telescope is pointed at a bright star, and a mask is placed in front of the telescope's objective (or in front of the aperture). The mask consists of three separate grids, positioned in such a way that the grids produce three angled diffraction spikes at the focal plane of the instrument for each bright image element. As the instrument's focus is changed, the central spike appears to move from one side of the star to the other. In reality, all three spikes move, but the central spike moves in the opposite direction to the two spikes forming the "X". Optimal focus is achieved when the middle spike is centered betwe ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
