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Hartmann Mask
Hartmann mask is a tool to help focusing telescopes, mainly used by amateur astronomers. It is named after the German astronomer Johannes Franz Hartmann (1865–1936), who developed it around 1900. Theory and practice Every part of a mirror or lens produces the same image as the whole optical element. The light is focused in the focal point. The light rays, however, go through different points of a plane before or behind the focus. This phenomenon can be used when focusing a telescope. The Hartmann mask is a simple opaque mask containing two or three holes. (This device is called a Hartmann mask if it has multiple holes, or a Scheiner disk if it has two holes.) The mask covers the aperture of the telescope. When the apparatus is out of focus, multiple images can be seen if the telescope is pointed towards a bright light source (Moon, bright star). Adjusting the focuser, the images can be made to overlap, forming a single bright, clear picture. The mask may also be used to che ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hartmann Screen
Hartmann is a Germanic and Ashkenazi Jewish surname. It is less frequently used as a male given name. The name originates from the Germanic word, "hart", which translates in English to "hardy", "hard", or "tough" and " Mann", a suffix meaning "man", "person", or "husband". The name Hartman, distinguished by ending with a single "n", is generally the result of the anglicisation of names that occurred with the emigration of persons from German-speaking to anglophone nations in the 18th, 19th and early 20th century. Below is a list of notable individuals and fictional characters with the surname or given name of Hartmann. Arts and media * Hartmann von Aue (c. 1170 – c. 1210) German poet * Lukas Hartmann (1944), Swiss novelist and children's literature writer * Manoah Hartmann, contestant on ''Canadian Idol'' (season 2) * Moritz Hartmann (1821–1872), German Jewish poet * Oluf Hartmann (1879–1910), Danish painter * Petra Hartmann (b 1970), German author and literature sc ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Focus Steps With Hartmann Mask
Focus, or its plural form foci may refer to: Arts * Focus or Focus Festival, former name of the Adelaide Fringe arts festival in South Australia Film *''Focus'', a 1962 TV film starring James Whitmore * ''Focus'' (2001 film), a 2001 film based on the Arthur Miller novel * ''Focus'' (2015 film), a 2015 film about con artists Music * Focus (music), a musical technique also known as modal frame * Focus..., American music producer * Focus (band), Dutch progressive rock band Albums * ''Focus'' (Stan Getz album), 1961 jazz album * ''Focus'' (Bill Hardman album), 1984 jazz album * ''Focus'' (Jan Akkerman & Thijs van Leer album), 1985 * ''Focus'' (Cynic album), 1993 metal album * ''Focus'' (Chico Freeman album), 1994 jazz album * ''Focus'' (Souls of Mischief album), 1998 alternative hip-hop album * ''Focus'' (Holly Starr album), 2012 CCM album * ''Focus'' (Arthur Blythe album), 2002 jazz album * ''Focus'' (Diaura album), 2013 Japanese visual kei album Songs * "Focus" (Ar ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Focus (optics)
In geometrical optics, a focus, also called an image point, is a point where light rays originating from a point on the object converge. Although the focus is conceptually a point, physically the focus has a spatial extent, called the blur circle. This non-ideal focusing may be caused by aberrations of the imaging optics. In the absence of significant aberrations, the smallest possible blur circle is the Airy disc, which is caused by diffraction from the optical system's aperture. Aberrations tend to worsen as the aperture diameter increases, while the Airy circle is smallest for large apertures. An image, or image point or region, is in focus if light from object points is converged almost as much as possible in the image, and out of focus if light is not well converged. The border between these is sometimes defined using a "circle of confusion" criterion. A principal focus or focal point is a special focus: * For a lens, or a spherical or parabolic mirror, it is a point ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Telescope
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 coin ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Johannes Franz Hartmann
Johannes Franz Hartmann (11 January 1865 – 13 September 1936) was a German physicist and astronomer. In 1904, while studying the spectroscopy of Delta Orionis he noticed that most of the spectrum had a shift, except the calcium lines, which he interpreted as indicating the presence of interstellar medium. Asimov, ''Asimov's Biographical Encyclopedia of Science and Technology'' 2nd Revised edition He was the director of the La Plata Astronomical Observatory, Argentina, from November 1922 to May 1934, and was also known under the name Juan Hartmann. He oriented the work of the observatory towards astrophysics and discovered the three asteroids of the main-belt, 965 Angelica, 1029 La Plata and 1254 Erfordia at La Plata between 1921 and 1932. His doctorate was from the University of Leipzig in 1891 on lunar eclipses. The lunar crater '' Hartmann'' on the far side of the Moon was named in his honor. Note, however, that the asteroid 3341 Hartmann was named after William ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mirror
A mirror or looking glass is an object that Reflection (physics), reflects an image. Light that bounces off a mirror will show an image of whatever is in front of it, when focused through the lens of the eye or a camera. Mirrors reverse the direction of the image in an equal yet opposite angle from which the light shines upon it. This allows the viewer to see themselves or objects behind them, or even objects that are at an angle from them but out of their field of view, such as around a corner. Natural mirrors have existed since prehistoric times, such as the surface of water, but people have been manufacturing mirrors out of a variety of materials for thousands of years, like stone, metals, and glass. In modern mirrors, metals like silver or aluminium are often used due to their high reflectivity, applied as a thin coating on glass because of its naturally smooth and very Hardness (materials science), hard surface. A mirror is a Wave (physics), wave reflector. Light consis ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Lens (optics)
A lens is a transmissive optical device which focuses or disperses a light beam by means of refraction. A simple lens consists of a single piece of transparent material, while a compound lens consists of several simple lenses (''elements''), usually arranged along a common axis. Lenses are made from materials such as glass or plastic, and are ground and polished or molded to a desired shape. A lens can focus light to form an image, unlike a prism, which refracts light without focusing. Devices that similarly focus or disperse waves and radiation other than visible light are also called lenses, such as microwave lenses, electron lenses, acoustic lenses, or explosive lenses. Lenses are used in various imaging devices like telescopes, binoculars and cameras. They are also used as visual aids in glasses to correct defects of vision such as myopia and hypermetropia. History The word ''lens'' comes from '' lēns'', the Latin name of the lentil (a seed of a lentil plant), ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Light
Light or visible light is electromagnetic radiation that can be perceived by the human eye. Visible light is usually defined as having wavelengths in the range of 400–700 nanometres (nm), corresponding to frequencies of 750–420 terahertz, between the infrared (with longer wavelengths) and the ultraviolet (with shorter wavelengths). In physics, the term "light" may refer more broadly to electromagnetic radiation of any wavelength, whether visible or not. In this sense, gamma rays, X-rays, microwaves and radio waves are also light. The primary properties of light are intensity, propagation direction, frequency or wavelength spectrum and polarization. Its speed in a vacuum, 299 792 458 metres a second (m/s), is one of the fundamental constants of nature. Like all types of electromagnetic radiation, visible light propagates by massless elementary particles called photons that represents the quanta of electromagnetic field, and can be analyzed as both waves and par ... [...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] |
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] |
Shack–Hartmann Wavefront Sensor
A Shack–Hartmann (or Hartmann–Shack) wavefront sensor (SHWFS) is an optical instrument used for characterizing an imaging system. It is a wavefront sensor commonly used in adaptive optics systems. It consists of an array of lenses (called lenslets) of the same focal length. Each is focused onto a photon sensor (typically a CCD array or CMOS array or quad-cell). If the sensor is placed at the geometric focal plane of the lenslet, and is uniformly illuminated, then, the integrated gradient of the wavefront across the lenslet is proportional to the displacement of the centroid. Consequently, any phase aberration can be approximated by a set of discrete tilts. By sampling the wavefront with an array of lenslets, all of these local tilts can be measured and the whole wavefront reconstructed. Since only tilts are measured the Shack–Hartmann cannot detect discontinuous steps in the wavefront. The design of this sensor improves upon an array of holes in a mask that had been dev ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Optical Devices
An optical instrument (or "optic" for short) is a device that processes light waves (or photons), either to enhance an image for viewing or to analyze and determine their characteristic properties. Common examples include periscopes, microscopes, telescopes, and cameras. Image enhancement The first optical instruments were telescopes used for magnification of distant images, and microscopes used for magnifying very tiny images. Since the days of Galileo and Van Leeuwenhoek, these instruments have been greatly improved and extended into other portions of the electromagnetic spectrum. The binocular device is a generally compact instrument for both eyes designed for mobile use. A camera could be considered a type of optical instrument, with the pinhole camera and camera obscura being very simple examples of such devices. Analysis Another class of optical instrument is used to analyze the properties of light or optical materials. They include: * Interferometer for measuring the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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