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Albert Bouwers
Albert A. Bouwers (1893–1972) was a Dutch optical engineer.Ian Ridpath, "Bouwers telescope", ''A Dictionary of Astronomy'', 199first sentence of article/ref> He is known for developing and working with X-rays and various optical technologies as a high-level researcher at Philips research labs. He is lesser known for patenting in 1941 a catadioptric meniscus telescope design similar to but slightly predating the Maksutov telescope. Biography Bouwers was born in the town of Dalen in the Netherlands in 1893.Reflecting Telescope Optics, by Ray N. Wilson, page 498Google Books, pg 498/ref> He obtained his Ph.D. from Utrecht University in 1924, with a dissertation entitled in Dutch ''Over het meten der intensiteit van Röntgenstralen''. He was also the director of the Philips Laboratory's X-ray department. Bouwers developed a night vision device for viewing in low light conditions, called the "night eye". Albert Bouwers built a prototype for a design for a wide field concentric me ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Brackets
A bracket is either of two tall fore- or back-facing punctuation marks commonly used to isolate a segment of text or data from its surroundings. They come in four main pairs of shapes, as given in the box to the right, which also gives their names, that vary between British English, British and American English. "Brackets", without further qualification, are in British English the ... marks and in American English the ... marks. Other symbols are repurposed as brackets in specialist contexts, such as International Phonetic Alphabet#Brackets and transcription delimiters, those used by linguists. Brackets are typically deployed in symmetric pairs, and an individual bracket may be identified as a "left" or "right" bracket or, alternatively, an "opening bracket" or "closing bracket", respectively, depending on the Writing system#Directionality, directionality of the context. In casual writing and in technical fields such as computing or linguistic analysis of grammar, brackets ne ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Russians
Russians ( ) are an East Slavs, East Slavic ethnic group native to Eastern Europe. Their mother tongue is Russian language, Russian, the most spoken Slavic languages, Slavic language. The majority of Russians adhere to Eastern Orthodox Church, Orthodox Christianity, ever since the Middle Ages. By total numbers, they compose the largest Slavs, Slavic and Ethnic groups in Europe, European nation. Genetic studies show that Russians are closely related to Polish people, Poles, Belarusians, Ukrainians, as well as Estonians, Latvians, Lithuanians, and Finns. They were formed from East Slavic tribes, and their cultural ancestry is based in Kievan Rus'. The Russian word for the Russians is derived from the Names of Rus', Russia and Ruthenia, people of Rus' and the territory of Rus'. Russians share many historical and cultural traits with other European peoples, and especially with other East Slavic ethnic groups, specifically Belarusians and Ukrainians. The vast majority of Russians ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Utrecht University Alumni
Utrecht ( ; ; ) is the List of cities in the Netherlands by province, fourth-largest city of the Netherlands, as well as the capital and the most populous city of the Provinces of the Netherlands, province of Utrecht (province), Utrecht. The municipality of Utrecht is located in the eastern part of the Randstad conurbation, in the very centre of mainland Netherlands, and includes Haarzuilens, Vleuten and De Meern. It has a population of 376,435 as of . Utrecht's ancient city centre features many buildings and structures, several dating as far back as the High Middle Ages. It has been the religious centre of the Netherlands since the 8th century. In 1579, the Union of Utrecht was signed in the city to lay the foundations for the Dutch Republic. Utrecht was the most important city in the Netherlands until the Dutch Golden Age, when it was surpassed by Amsterdam as the country's cultural centre and most populous city. Utrecht is home to Utrecht University, the largest university ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
People From Coevorden
The term "the people" refers to the public or Common people, common mass of people of a polity. As such it is a concept of human rights law, international law as well as constitutional law, particularly used for claims of popular sovereignty. In contrast, a people is any plurality of Person, persons considered as a whole. Used in politics and law, the term "a people" refers to the collective or community of an ethnic group or nation. Concepts Legal Chapter One, Article One of the Charter of the United Nations states that "peoples" have the right to self-determination. Though the mere status as peoples and the right to self-determination, as for example in the case of Declaration on the Rights of Indigenous Peoples, Indigenous peoples (''peoples'', as in all groups of indigenous people, not merely all indigenous persons as in ''indigenous people''), does not automatically provide for independence, independent sovereignty and therefore secession. Indeed, judge Ivor Jennings i ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
1972 Deaths
Within the context of Coordinated Universal Time (UTC) it was the longest year ever, as two leap seconds were added during this 366-day year, an event which has not since been repeated. (If its start and end are defined using Solar time, mean solar time [the legal time scale], its duration was 31622401.141 seconds of Terrestrial Time (or Ephemeris Time), which is slightly shorter than 1908 in science#Astronomy, 1908). Events January * January 1 – Kurt Waldheim becomes Secretary-General of the United Nations. * January 4 – The first scientific hand-held calculator (HP-35) is introduced (price $395). * January 7 – Iberia Airlines Flight 602 crashes into a 462-meter peak on the island of Ibiza; 104 are killed. * January 9 – The RMS Queen Elizabeth, RMS ''Queen Elizabeth'' catches fire and sinks in Hong Kong's Victoria harbor while undergoing conversion to a floating university. * January 10 – Independence leader Sheikh Mujibur Rahman returns to Bangladesh after s ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
1893 Births
Events January * January 2 – Webb C. Ball introduces railroad chronometers, which become the general railroad timepiece standards in North America. * January 6 – The Washington National Cathedral is chartered by Congress; the charter is signed by President Benjamin Harrison. * January 13 ** The Independent Labour Party of the United Kingdom has its first meeting. ** U.S. Marines from the ''USS Boston'' land in Honolulu, Hawaii, to prevent the queen from abrogating the Bayonet Constitution. * January 15 – The '' Telefon Hírmondó'' service starts with around 60 subscribers, in Budapest. * January 17 – Overthrow of the Kingdom of Hawaii: Lorrin A. Thurston and the Citizen's Committee of Public Safety in Hawaii, with the intervention of the United States Marine Corps, overthrow the government of Queen Liliuokalani. * January 21 – The Tati Concessions Land, formerly part of Matabeleland, is formally annexed to the Bechuanaland Protec ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Doublet (lens)
In optics, a doublet is a type of lens made up of two simple lenses paired together. Such an arrangement allows more optical surfaces, thicknesses, and formulations, especially as the space between lenses may be considered an "element". With additional degrees of freedom, optical designers have more latitude to correct more optical aberrations more thoroughly. Types Doublets can come in many forms, though most commercial doublets are achromats, which are optimized to reduce chromatic aberration while also reducing spherical aberration and other optical aberrations. The lenses are made from glasses with different refractive indices and different amounts of dispersion. Often one element is a positive lens made of crown glass and the other is a negative lens made of flint glass. This combination produces a better image than a simple lens. Some Trilobites, which are now extinct, had natural doublet lenses in their eyes. Apochromats can also be made as doublets. Doublet ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Wavelength Of Light
In physics and mathematics, wavelength or spatial period of a wave or periodic function is the distance over which the wave's shape repeats. In other words, it is the distance between consecutive corresponding points of the same ''phase'' on the wave, such as two adjacent crests, troughs, or zero crossings. Wavelength is a characteristic of both traveling waves and standing waves, as well as other spatial wave patterns. The inverse of the wavelength is called the ''spatial frequency''. Wavelength is commonly designated by the Greek letter lambda (''λ''). For a modulated wave, ''wavelength'' may refer to the carrier wavelength of the signal. The term ''wavelength'' may also apply to the repeating envelope of modulated waves or waves formed by interference of several sinusoids. Assuming a sinusoidal wave moving at a fixed wave speed, wavelength is inversely proportional to the frequency of the wave: waves with higher frequencies have shorter wavelengths, and lower frequencies ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Astrograph
An astrograph (or astrographic camera) is a telescope designed for the sole purpose of astrophotography. Astrographs are mostly used in wide-field astronomical surveys of the sky and for detection of objects such as asteroids, meteors, and comets. Improvements in photography in the middle 19th century led to designs dedicated to astrophotography, and they were also popular in the 20th century. As in other photography, chemicals were used that respond to light, recorded on a glass photographic plate or sometimes on photographic film. Many observatories of this period used an astrograph, beside instruments like the transit telescope, great refractors, and chronometers, or instruments for observing the Sun. Astrographs were often used to make surveys of the night sky, and one of the famous projects was Carte du Ciel. Discoveries using an astrograph include then-planet Pluto. Rather than looking through the telescope, it was discovered by using a blink comparator with ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Chromatic Aberration
In optics, chromatic aberration (CA), also called chromatic distortion, color aberration, color fringing, or purple fringing, 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. Since the focal length of the lens varies with the color of the light different colors of light are brought to focus at different distances from the lens or with different levels of magnification. 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 wavelengt ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Aperture Stop
In optics, the aperture of an optical system (including a system consisting of a single lens) is the hole or opening that primarily limits light propagated through the system. More specifically, the entrance pupil as the front side image of the aperture and focal length of an optical system determine the cone angle of a bundle of ray (optics), rays that comes to a focus (optics), focus in the image plane. An optical system typically has many structures that limit ray bundles (ray bundles are also known as ''pencils'' of light). These structures may be the edge of a lens (optics), 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 (optics), 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 cone of rays that an optical system accepts (see entrance pupil). As a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Meniscus Corrector
A meniscus corrector is a negative meniscus lens that is used to correct spherical aberration in image-forming optical systems such as catadioptric telescopes. It works by having the equal but opposite spherical aberration of the objective it is designed to correct (usually a spherical mirror). Types Meniscus correctors are used as full aperture correctors, most commonly in a Maksutov telescope sub type called the Gregory or “spot” Maksutov–Cassegrain telescope. They are also used in the Bouwers meniscus telescope. There are Maksutov variations that use the same principle but place the meniscus lens as a sub-aperture corrector near the focus of the objective. There are other sub-aperture meniscus corrector catadioptric telescopes such as the Argunov–Cassegrain telescope and the Klevtsov–Cassegrain telescope. Invention The idea of using the spherical aberration of a meniscus lens to correct the opposite aberration in a spherical objective dates back as far as W. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
