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Bouwers Meniscus Telescope
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 meniscu ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dutch People
The Dutch (Dutch: ) are an ethnic group and nation native to the Netherlands. They share a common history and culture and speak the Dutch language. Dutch people and their descendants are found in migrant communities worldwide, notably in Aruba, Suriname, Guyana, Curaçao, Argentina, Brazil, Canada,Based on Statistics Canada, Canada 2001 Censusbr>Linkto Canadian statistics. Australia, South Africa, New Zealand and the United States.According tFactfinder.census.gov The Low Countries were situated around the border of France and the Holy Roman Empire, forming a part of their respective peripheries and the various territories of which they consisted had become virtually autonomous by the 13th century. Under the Habsburgs, the Netherlands were organised into a single administrative unit, and in the 16th and 17th centuries the Northern Netherlands gained independence from Spain as the Dutch Republic. The high degree of urbanization characteristic of Dutch society was attained at a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Russians
, native_name_lang = ru , image = , caption = , population = , popplace = 118 million Russians in the Russian Federation (2002 ''Winkler Prins'' estimate) , region1 = , pop1 = approx. 7,500,000 (including Russian Jews and Russian Germans) , ref1 = , region2 = , pop2 = 7,170,000 (2018) ''including Crimea'' , ref2 = , region3 = , pop3 = 3,512,925 (2020) , ref3 = , region4 = , pop4 = 3,072,756 (2009)(including Russian Jews and Russian Germans) , ref4 = , region5 = , pop5 = 1,800,000 (2010)(Russian ancestry and Russian Germans and Jews) , ref5 = 35,000 (2018)(born in Russia) , region6 = , pop6 = 938,500 (2011)(including Russian Jews) , ref6 = , region7 = , pop7 = 809,530 (2019) , ref7 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Utrecht University Alumni
Utrecht ( , , ) is the fourth-largest city and a municipality of the Netherlands, capital and most populous city of the province of Utrecht. It is located in the eastern corner of the Randstad conurbation, in the very centre of mainland Netherlands, about 35 km south east of the capital Amsterdam and 45 km north east of Rotterdam. It has a population of 361,966 as of 1 December 2021. 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. It 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 in the Netherlands, as well as several other institutions of higher education. Due to its central position within the country, it is an important hub for both rail and road t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
People From Coevorden
A person ( : people) is a being that has certain capacities or attributes such as reason, morality, consciousness or self-consciousness, and being a part of a culturally established form of social relations such as kinship, ownership of property, or legal responsibility. The defining features of personhood and, consequently, what makes a person count as a person, differ widely among cultures and contexts. In addition to the question of personhood, of what makes a being count as a person to begin with, there are further questions about personal identity and self: both about what makes any particular person that particular person instead of another, and about what makes a person at one time the same person as they were or will be at another time despite any intervening changes. The plural form "people" is often used to refer to an entire nation or ethnic group (as in "a people"), and this was the original meaning of the word; it subsequently acquired its use as a plural form of ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
1972 Deaths
Year 197 ( CXCVII) was a common year starting on Saturday (link will display the full calendar) of the Julian calendar. At the time, it was known as the Year of the Consulship of Magius and Rufinus (or, less frequently, year 950 '' Ab urbe condita''). The denomination 197 for this year has been used since the early medieval period, when the Anno Domini calendar era became the prevalent method in Europe for naming years. Events By place Roman Empire * February 19 – Battle of Lugdunum: Emperor Septimius Severus defeats the self-proclaimed emperor Clodius Albinus at Lugdunum (modern Lyon). Albinus commits suicide; legionaries sack the town. * Septimius Severus returns to Rome and has about 30 of Albinus's supporters in the Senate executed. After his victory he declares himself the adopted son of the late Marcus Aurelius. * Septimius Severus forms new naval units, manning all the triremes in Italy with heavily armed troops for war in the East. His soldiers embark ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
1893 Births
Events January–March * January 2 – Webb C. Ball introduces railroad chronometers, which become the general railroad timepiece standards in North America. * Mark Twain started writing Puddn'head Wilson. * 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 Cherry Sisters first perform in Marion, Iowa. ** The T ... [...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 made from crown glass and the other from 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. Doublets can be air-spaced, cemented, or "oiled". Oi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Wavelength Of Light
In physics, the wavelength is the spatial period of a periodic wave—the distance over which the wave's shape repeats. It is the distance between consecutive corresponding points of the same phase (waves), phase on the wave, such as two adjacent crests, troughs, or zero crossings, and is a characteristic of both traveling waves and standing waves, as well as other spatial wave patterns. The multiplicative inverse, inverse of the wavelength is called the spatial frequency. Wavelength is commonly designated by the Greek letter ''lambda'' (λ). The term ''wavelength'' is also sometimes applied to modulation, modulated waves, and to the sinusoidal envelope (mathematics), envelopes of modulated waves or waves formed by Interference (wave propagation), interference of several sinusoids. Assuming a sinusoidal wave moving at a fixed wave speed, wavelength is inversely proportional to 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 im ... [...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] |
Aperture Stop
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] |
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. F. Hamil ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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