In photography, a shutter is a device that allows light to pass for a determined period, exposing photographic film or a photosensitive digital sensor to light in order to capture a permanent image of a scene. A shutter can be used to allow pulses of light to pass outwards, as seen in a movie projector or a signal lamp. A shutter of variable speed is used to control exposure time of the film; the shutter is constructed. The speed of the shutter is controlled by a ring outside the camera, on which various timings are marked. Camera shutters can be fitted in several positions: Leaf shutters are fitted within a lens assembly, or more immediately behind or more in front of a lens, shut off the beam of light where it is narrow. Focal-plane shutters are mounted near move to uncover the film or sensor. Behind-the-lens shutters were used in some cameras with limited lens interchangeability. Shutters in front of the lens, sometimes a lens cap, removed and replaced for the long exposures required, were used in the early days of photography.
Other mechanisms than the dilating aperture and the sliding curtains have been used. The time for which a shutter remains open is determined by a timing mechanism; these were pneumatic or clockwork, but since the late twentieth century are electronic. Mechanical shutters had a Time setting, where the shutter opened when the button was pressed and remained open until it was pressed again, Bulb where the shutter remained open as long as the button was pressed, Instantaneous exposure, with settings ranging from 30" to 1/4000" for the best leaf shutters, faster for focal-plane shutters, more restricted for basic types; the reciprocal of exposure time in seconds is used for engraving shutter settings. For example, a marking of "250" denotes 1/250"; this does not cause confusion in practice. The exposure time and the effective aperture of the lens must together be such as to allow the right amount of light to reach the film or sensor. Additionally, the exposure time must be suitable to handle any motion of the subject.
It must be fast enough to "freeze" rapid motion, unless a controlled degree of motion blur is desired, for example to give a sensation of movement. Most shutters have a flash synchronization switch to trigger a flash; this was quite a complicated matter with mechanical shutters and flashbulbs which took an appreciable time to reach full brightness, focal-plane shutters making this more difficult. Special flashbulbs were designed which had a prolonged burn, illuminating the scene for the whole time taken by a focal plane shutter slit to move across the film; these problems were solved for non-focal-plane shutters with the advent of electronic flash units which fire instantaneously and emit a short flash. When using a focal-plane shutter with a flash, if the shutter is set at its X-sync speed or slower the whole frame will be exposed when the flash fires; some electronic flashes can produce a longer pulse compatible with a focal-plane shutter operated at much higher shutter speeds. The focal-plane shutter will still impart focal-plane shutter distortions to a moving subject.
Cinematography uses a rotary disc shutter in movie cameras, a continuously spinning disc which conceals the image with a reflex mirror during the intermittent motion between frame exposure. The disc spins to an open section that exposes the next frame of film while it is held by the registration pin. A focal-plane shutter is positioned just in front of the film, in the focal plane, moves an aperture across the film until the full frame has been exposed. Focal-plane shutters are implemented as a pair of light-tight cloth, metal, or plastic curtains. For shutter speeds slower than a certain point, which depends on the camera, one curtain of the shutter opens, the other closes after the correct exposure time. At shutter speeds faster than the X-sync speed, the top curtain of the shutter travels across the focal plane, with the second curtain following behind moving a slit across the focal plane until each part of the film or sensor has been exposed for the correct time; the effective exposure time can be much shorter than for central shutters, at the cost of some distortion of fast-moving subjects.
Focal plane shutters have the advantage over central leaf shutters of allowing the use of interchangeable lenses without requiring a separate shutter for each lens. They have several disadvantages as well: Distortion of fast-moving subjects: although no part of the film is exposed for longer than the time set on the dial, one edge of the film is exposed an appreciable time after the other, so that a horizontally moving shutter will, for example, elongate or shorten the image of a car speeding in the same or the opposite direction to the shutter movement, they are noisier, a detriment to candid and nature photography. Their more complex mechanical structure causes a shorter life-span than other shutter designs. If a focal-plane shutter camera is left with sunlight falling on the lens, it is possible to burn a hole in the closed curtain of a non-metal shutter. Camera shake due to the impact of the larger curtains stopping rapidly. Camera designers
In photography, shutter speed or exposure time is the length of time when the film or digital sensor inside the camera is exposed to light when a camera's shutter is open when taking a photograph. The amount of light that reaches the film or image sensor is proportional to the exposure time. 1⁄500 of a second will let half as much light in as 1⁄250. The camera's shutter speed, the lens's aperture, the Film Speed, the scene's luminance together determine the amount of light that reaches the film or sensor. Exposure value is a quantity that accounts for the f-number. Once the sensitivity to light of the recording surface is set in numbers expressed in "ISOs", the light emitted by the scene photographed can be controlled through aperture and shutter-speed to match the film or sensor sensitivity to light; this will achieve a good exposure. Too much light let into the camera results in an overly pale image while too little light will result in an overly dark image. Multiple combinations of shutter speed and f-number can give the same exposure value.
According to exposure value formula, doubling the exposure time doubles the amount of light. Reducing the aperture size at multiples of one over the square root of two lets half as much light into the camera at a predefined scale of f/1, f/1.4, f/2, f/2.8, f/4, f/5.6, f/8, f/11, f/16, f/22, so on. For example, f/8 lets 4 times more light into the camera. A shutter speed of 1⁄50 s with an f/4 aperture gives the same exposure value as a 1⁄100 s shutter speed with an f/2.8 aperture, the same exposure value as a 1⁄200 s shutter speed with an f/2 aperture, or 1⁄25 s at f/5.6. In addition to its effect on exposure, the shutter speed changes the way movement appears in photographs. Short shutter speeds can be used to freeze fast-moving subjects, for example at sporting events. Long shutter speeds are used to intentionally blur a moving subject for effect. Short exposure times are sometimes called "fast", long exposure times "slow". Adjustments to the aperture need to be compensated by changes of the shutter speed to keep the same exposure.
In early days of photography, available shutter speeds were not standardized, though a typical sequence might have been 1⁄10 s, 1⁄25 s, 1⁄50 s, 1⁄100 s, 1⁄200 s and 1⁄500 s. Soon this problem resulted in a solution consisting in the adoption of a standardized way of choosing aperture so that each major step doubled or halved the amount of light entering the camera, a standardized 2:1 scale was adopted for shutter speed so that opening one aperture stop and reducing the amount of time of the shutter speed by one step resulted in the identical exposure; the agreed standards for shutter speeds are: With this scale, each increment doubles the amount of light or halves it. Camera shutters include one or two other settings for making long exposures: B keeps the shutter open as long as the shutter release is held. T keeps the shutter open; the ability of the photographer to take images without noticeable blurring by camera movement is an important parameter in the choice of the slowest possible shutter speed for a handheld camera.
The rough guide used by most 35 mm photographers is that the slowest shutter speed that can be used without much blur due to camera shake is the shutter speed numerically closest to the lens focal length. For example, for handheld use of a 35 mm camera with a 50 mm normal lens, the closest shutter speed is 1⁄60 s, while for a 200 mm lens it is recommended not to choose shutter speeds below 1⁄200 of a second; this rule can be augmented with knowledge of the intended application for the photograph, an image intended for significant enlargement and closeup viewing would require faster shutter speeds to avoid obvious blur. Through practice and special techniques such as bracing the camera, arms, or body to minimize camera movement, using a monopod or a tripod, slower shutter speeds can be used without blur. If a shutter speed is too slow for hand holding, a camera support a tripod, must be used. Image stabilization on digital cameras or lenses can permit the use of shutter speeds 3–4 stops slower.
Shutter priority refers to a shooting mode used in cameras. It allows the photographer to choose a shutter speed setting and allow the camera to decide the correct aperture; this is sometimes referred to as Shutter Speed Priority Auto Exposure, or TV mode, S mode on Nikons and most other brands. Shutter speed is one of several methods used to control the amount of light recorded by the camera's digital sensor or film, it is used to manipulate the visual effects of the final image. Slower shutter speeds are selected to suggest the movement of an object in a still photograph. Excessively fast shutter speeds can cause a moving subject to appear unnaturally frozen. For instance, a running person may be caught with both feet in the air with all indication of movement lost in the frozen moment; when a slower shutter speed is selected, a longer time passes from the moment the shutter opens till the moment it closes. More time is available for movement in the subject to be recorded by the camera as a blur.
A slower shutter speed will allow the photographer to introd
Film speed is the measure of a photographic film's sensitivity to light, determined by sensitometry and measured on various numerical scales, the most recent being the ISO system. A related ISO system is used to describe the relationship between exposure and output image lightness in digital cameras. Insensitive film, with a correspondingly lower speed index, requires more exposure to light to produce the same image density as a more sensitive film, is thus termed a slow film. Sensitive films are correspondingly termed fast films. In both digital and film photography, the reduction of exposure corresponding to use of higher sensitivities leads to reduced image quality. In short, the higher the sensitivity, the grainier the image will be. Sensitivity is limited by the quantum efficiency of the film or sensor; the first known practical sensitometer, which allowed measurements of the speed of photographic materials, was invented by the Polish engineer Leon Warnerke – pseudonym of Władysław Małachowski – in 1880, among the achievements for which he was awarded the Progress Medal of the Photographic Society of Great Britain in 1882.
It was commercialized since 1881. The Warnerke Standard Sensitometer consisted of a frame holding an opaque screen with an array of 25 numbered pigmented squares brought into contact with the photographic plate during a timed test exposure under a phosphorescent tablet excited before by the light of a burning magnesium ribbon; the speed of the emulsion was expressed in'degrees' Warnerke corresponding with the last number visible on the exposed plate after development and fixation. Each number represented an increase of 1/3 in speed, typical plate speeds were between 10° and 25° Warnerke at the time, his system saw some success but proved to be unreliable due to its spectral sensitivity to light, the fading intensity of the light emitted by the phosphorescent tablet after its excitation as well as high built-tolerances. The concept, was built upon in 1900 by Henry Chapman Jones in the development of his plate tester and modified speed system. Another early practical system for measuring the sensitivity of an emulsion was that of Hurter and Driffield described in 1890, by the Swiss-born Ferdinand Hurter and British Vero Charles Driffield.
In their system, speed numbers were inversely proportional to the exposure required. For example, an emulsion rated at 250 H&D would require ten times the exposure of an emulsion rated at 2500 H&D; the methods to determine the sensitivity were modified in 1925 and in 1928 —this variant was sometimes called "H&D 10". The H&D system was accepted as a standard in the former Soviet Union from 1928 until September 1951, when it was superseded by GOST 2817-50; the Scheinergrade system was devised by the German astronomer Julius Scheiner in 1894 as a method of comparing the speeds of plates used for astronomical photography. Scheiner's system rated the speed of a plate by the least exposure to produce a visible darkening upon development. Speed was expressed in degrees Scheiner ranging from 1° Sch. to 20° Sch. where an increment of 19° Sch. corresponded to a hundredfold increase in sensitivity, which meant that an increment of 3° Sch. came close to a doubling of sensitivity. 100 19 3 = 2.06914... ≈ 2 The system was extended to cover larger ranges and some of its practical shortcomings were addressed by the Austrian scientist Josef Maria Eder and Flemish-born botanist Walter Hecht.
Still, it remained difficult for manufactures to reliably determine film speeds only by comparing with competing products, so that an increasing number of modified semi-Scheiner-based systems started to spread, which no longer followed Scheiner's original procedures and thereby defeated the idea of comparability. Scheiner's system was abandoned in Germany, when the standardized DIN system was introduced in 1934. In various forms, it continued to be in widespread use in other countries for some time; the DIN system DIN standard 4512 by Deutsches Institut für Normung, was published in January 1934. It grew out of drafts for a standardized method of sensitometry put forward by Deutscher Normenausschuß für Phototechnik as proposed by the committee for sensitometry of the Deutsche Gesellschaft für photographische Forschung since 1930 and presented by Robert Luther and Emanuel Goldberg at the influential VIII. International Congress of Photography held in Dresden from August 3 to 8, 1931; the DIN system was inspired by Scheiner's system, but the sensitivities were represented as the base 10 logarithm of the sensitivity multiplied by 10, similar to decibels.
Thus an increase of 20° represented a hundredfold increase in sensitivity, a difference of 3° was much closer to the base 10 logarithm of 2: log 10 = 0.30103... ≈ 3 / 10 As in the Sche
Mount Wellington (Tasmania)
Mount Wellington kunanyi / Mount Wellington, incorporating its Palawa kani name, is a mountain in the southeast coastal region of Tasmania, Australia. It is within the Wellington Park reserve. Located at the foothills of the mountain is much of Tasmania's capital city, Hobart; the mountain rises to 1,271 metres above sea level and is covered by snow, sometimes in summer, the lower slopes are thickly forested, but crisscrossed by many walking tracks and a few fire trails. There is a sealed narrow road to the summit, about 22 kilometres from Hobart central business district. An enclosed lookout near the summit has views of the city below and to the east, the Derwent estuary, glimpses of the World Heritage Area nearly 100 kilometres west. From Hobart, the most distinctive feature of Mount Wellington is the cliff of dolerite columns known as the Organ Pipes; the low-lying areas and foothills of Mount Wellington were formed by slow geological upsurge when the whole Hobart area was a low-lying cold shallow seabed.
The upper reaches of the mountain were formed more violently, as a Sill with a tabular mass of igneous rock, intruded laterally between layers of older rock pushing upwards by upsurges of molten rock as the Australian continental shelf tore away from Antarctica, separated from Gondwana over 40 million years ago. It is incorrectly considered to be a dormant volcano. Mount Wellington was referred by the original Tasmanian nations of the area as Unghbanyahletta, Poorawetter, or kunanyi to the indigenous people of Tasmania; the Palawa, the surviving descendants of the original indigenous Tasmanians, tend to prefer the latter name. In 2013, a Tasmanian dual naming policy was announced and "kunanyi / Mount Wellington" was named as one of the inaugural dual named geographic features; the first recorded European in the area Abel Tasman did not see the mountain in 1642, as his ship was quite a distance out to sea as he sailed up the South East coast of the island – coming closer in near present-day North and Marion Bays.
No other Europeans visited Tasmania until the late eighteenth century, when several visited southern Tasmania including Frenchman Marion du Fresne, Englishmen Tobias Furneaux, James Cook and William Bligh, Frenchman Bruni d'Entrecasteaux. In 1793 Commodore John Hayes arrived at the Derwent River, naming the mountain Skiddaw, after the mountain in the Lake District, although this name never gained popularity. In 1798 Matthew Flinders and George Bass circumnavigated the island. Whilst they were resting in the area Flinders named the river the Derwent River, Flinders referred to the mountain as ‘Table Mountain’ for its similarity in appearance to Table Mountain in South Africa. Bruni d'Entrecasteaux's men were the first European to chart it. Nicholas Baudin led another French expedition in 1802, whilst sheltering in the Derwent River Baudin referred to the mountain as ‘Montagne du Plateau’. However, the British first settled in the Hobart area in 1804, resulting in Flinders’ name of ‘Table Mountain’ becoming more popular.
Table Mountain remained its common name until in 1832 it was decided to rename the mountain in honour of the Duke of Wellington who, with Gebhard Leberecht von Blücher defeated Napoleon at the Battle of Waterloo in present-day Belgium on 18 June 1815. In February 1836, Charles Darwin climbed Mount Wellington. In his book "The Voyage of the Beagle", Darwin described the mountain thus. In many parts the Eucalypti grew to a great size, composed a noble forest. In some of the dampest ravines, tree-ferns flourished in an extraordinary manner; the fronds forming the most elegant parasols, produced a gloomy shade, like that of the first hour of the night. The summit of the mountain is broad and flat, is composed of huge angular masses of naked greenstone, its elevation is 3,100 feet above the level of the sea. The day was splendidly clear, we enjoyed a most extensive view; the first weather station was set up on Mount Wellington in 1895 by Clement Lindley Wragge. Mount Wellington has played host to some notorious characters over time the bushranger'Rocky' Whelan, who murdered several travelers in the middle of the 19th century.
The cave where he lived is known appropriately as'Rocky Whelan's Cave', is an easy walk from the Springs. Throughout the 19th and into the 20th centuries, the Mountain was a popular day-resort for residents of Hobart. To that end, many excursion huts were built over the lower slopes of the mountain. However, none of these early huts survive as they were all destroyed during the disastrous bushfires of 1967, though modern huts are open to the public at the Springs, the Pinnacle, the Chalet – a picnic spot about halfway between the Springs and the Pinnacle – and elsewhere. Sadly, many of the more remote huts have suffered from vandalism, s
Low Earth orbit
A Low Earth Orbit is an Earth-centered orbit with an altitude of 2,000 km or less, or with at least 11.25 periods per day and an eccentricity less than 0.25. Most of the manmade objects in space are in LEO. A histogram of the mean motion of the cataloged objects shows that the number of objects drops beyond 11.25. There is a large variety of other sources; the altitude of an object in an elliptic orbit can vary along the orbit. For circular orbits, the altitude above ground can vary by as much as 30 km due to the oblateness of Earth's spheroid figure and local topography. While definitions in terms of altitude are inherently ambiguous, most of them fall within the range specified by an orbit period of 128 minutes because, according to Kepler's third law, this corresponds to a semi-major axis of 8,413 km. For circular orbits, this in turn corresponds to an altitude of 2,042 km above the mean radius of Earth, consistent with some of the upper limits in the LEO definitions in terms of altitude; the LEO region is defined by some sources as the region in space.
Some elliptical orbits may pass through the LEO region near their lowest altitude but are not in an LEO Orbit because their highest altitude exceeds 2,000 km. Sub-orbital objects can reach the LEO region but are not in an LEO orbit because they re-enter the atmosphere; the distinction between LEO orbits and the LEO region is important for analysis of possible collisions between objects which may not themselves be in LEO but could collide with satellites or debris in LEO orbits. The International Space Station conducts operations in LEO. All crewed space stations to date, as well as the majority of satellites, have been in LEO; the altitude record for human spaceflights in LEO was Gemini 11 with an apogee of 1,374.1 km. Apollo 8 was the first mission to carry humans beyond LEO on December 21–27, 1968; the Apollo program continued during the four-year period spanning 1968 through 1972 with 24 astronauts who flew lunar flights but since there have been no human spaceflights beyond LEO. The mean orbital velocity needed to maintain a stable low Earth orbit is about 7.8 km/s, but reduces with increased orbital altitude.
Calculated for circular orbit of 200 km it is 7.79 km/s and for 1500 km it is 7.12 km/s. The delta-v needed to achieve low Earth orbit starts around 9.4 km/s. Atmospheric and gravity drag associated with launch adds 1.3–1.8 km/s to the launch vehicle delta-v required to reach normal LEO orbital velocity of around 7.8 km/s. The pull of gravity in LEO is only less than on the earth's surface; this is. However, an object in orbit is, in free fall, since there is no force holding it up; as a result objects in orbit, including people, experience a sense of weightlessness though they are not without weight. Objects in LEO encounter atmospheric drag from gases in the thermosphere or exosphere, depending on orbit height. Due to atmospheric drag, satellites do not orbit below 300 km. Objects in LEO orbit Earth between the denser part of the atmosphere and below the inner Van Allen radiation belt. Equatorial low Earth orbits are a subset of LEO; these orbits, with low inclination to the Equator, allow rapid revisit times and have the lowest delta-v requirement of any orbit.
Orbits with a high inclination angle to the equator are called polar orbits. Higher orbits include medium Earth orbit, sometimes called intermediate circular orbit, further above, geostationary orbit. Orbits higher than low orbit can lead to early failure of electronic components due to intense radiation and charge accumulation. In 2017, a very-low LEO orbit began to be seen in regulatory filings; this orbit, referred to as "VLEO", requires the use of novel technologies for orbit raising because they operate in orbits that would ordinarily decay too soon to be economically useful. A low Earth orbit requires the lowest amount of energy for satellite placement, it provides low communication latency. Satellites and space stations in LEO are more accessible for servicing. Since it requires less energy to place a satellite into a LEO, a satellite there needs less powerful amplifiers for successful transmission, LEO is used for many communication applications, such as the Iridium phone system; some communication satellites use much higher geostationary orbits, move at the same angular velocity as the Earth as to appear stationary above one location on the planet.
Satellites in LEO have a small momentary field of view, only able to observe and communicate with a fraction of the Earth at a time, meaning a network of satellites is required to in order to provide continuous coverage. Satellites in lower regions of LEO suffer from fast orbital decay, requiring either periodic reboosting to maintain a stable orbit, or launching replacement satellites when old ones re-enter. Earth observation satellites and spy satellites use LEO as they are able to see the surface of the Earth by being close to it, they are able to traverse the surface of the Earth. A majority of artificial satellites are placed in LEO, making one complete revolution around the Earth in about 90 minutes; the International Space Station is in a LEO about 330 km to 420 km above Earth's surfac
Cassiopeia is a constellation in the northern sky, named after the vain queen Cassiopeia in Greek mythology, who boasted about her unrivaled beauty. Cassiopeia was one of the 48 constellations listed by the 2nd-century Greek astronomer Ptolemy, it remains one of the 88 modern constellations today, it is recognizable due to its distinctive'W' shape, formed by five bright stars. It is opposite Ursa Major. In northern locations above latitude 34ºN it is visible year-round and in the tropics it can be seen at its clearest from September to early November. In low southern latitudes below 25ºS it can be seen low in the North. At magnitude 2.2, Alpha Cassiopeiae, or Schedar, is the brightest star in Cassiopeia, though is shaded by Gamma Cassiopeiae, which has brightened to magnitude 1.6 on occasion. The constellation hosts some of the most luminous stars known, including the yellow hypergiants Rho Cassiopeiae and V509 Cassiopeiae and white hypergiant 6 Cassiopeiae; the semiregular variable. In 1572, Tycho Brahe's supernova flared brightly in Cassiopeia.
Cassiopeia A is a supernova remnant and the brightest extrasolar radio source in the sky at frequencies above 1 GHz. Fourteen star systems have been found to have exoplanets, one of which—HR 8832—is thought to host seven planets. A rich section of the Milky Way runs through Cassiopeia, containing a number of open clusters, young luminous galactic disc stars, nebulae. IC 10 is an irregular galaxy, the closest known starburst galaxy and the only one in the Local Group of galaxies; the constellation is named after the queen of Aethiopia. Cassiopeia was the wife of mother of Princess Andromeda. Cepheus and Cassiopeia were placed next to each other among the stars, along with Andromeda, she was placed in the sky as a punishment after enraging Poseidon with the boast that her daughter Andromeda was more beautiful than the Nereids or, that she herself was more beautiful than the sea nymphs. She was forced to wheel around the North Celestial Pole on her throne, spending half of her time clinging to it so she does not fall off, Poseidon decreed that Andromeda should be bound to a rock as prey for the monster Cetus.
Andromeda was rescued by the hero Perseus, whom she married. Cassiopeia has been variously portrayed throughout her history as a constellation. In Persia, she was drawn by al-Sufi as a queen holding a staff with a crescent moon in her right hand, wearing a crown, as well as a two-humped camel. In France, she was portrayed as having a marble throne and a palm leaf in her left hand, holding her robe in her right hand; this depiction is from Augustin Royer's 1679 atlas. In Chinese astronomy, the stars forming the constellation Cassiopeia are found among three areas: the Purple Forbidden enclosure, the Black Tortoise of the North, the White Tiger of the West; the Chinese astronomers saw several figures in. Kappa, Mu Cassiopeiae formed a constellation called the Bridge of the Kings; the charioteer's whip was represented by Gamma Cassiopeiae, sometimes called "Tsih", the Chinese word for "whip". In the 1600s, various Biblical figures were depicted in the stars of Cassiopeia; these included Solomon's mother.
A figure called the "Tinted Hand" appeared in the stars of Cassiopeia in some Arab atlases. This is variously said to represent a woman's hand dyed red with henna, as well as the bloodied hand of Muhammad's daughter Fatima; the hand is made up of the stars α Cas, β Cas, γ Cas, δ Cas, ε Cas, η Cas. The arm is made up of the stars α Per, γ Per, δ Per, ε Per, η Per, ν Per. Another Arab constellation that incorporated the stars of Cassiopeia was the Camel, its head was composed of Lambda, Kappa and Phi Andromedae. Other cultures see a moose antlers in the pattern; these include the Lapps. The Chukchi of Siberia saw the five main stars as five reindeer stags; the people of the Marshall Islands saw Cassiopeia as part of a great porpoise constellation. The main stars of Cassiopeia make its tail and Triangulum form its body, Aries makes its head. In Hawaii, Alpha and Gamma Cassiopeiae were named. Alpha Cassiopeiae was called Poloahilani, Beta Cassiopeiae was called Polula, Gamma Cassiopeiae was called Mulehu.
The people of Pukapuka saw the figure of Cassiopeia as a distinct constellation called Na Taki-tolu-a-Mataliki. In Modern Indian Astronomy Cassiopeia is known as Sharmishtha. In Hindu mythology, Sharmistha known as Sharmista or Sharmishtha, was the daughter of the great Devil King Vrishparva, she was a friend of Devayani for whom she becomes a servant. Covering 598.4 square degrees and hence 1.451% of the sky, Cassiopeia ranks 25th of the 88 constellations in area. It is bordered by Cepheus to the north and west, Andromeda to the south and west, Perseus to the southeast and Camelopardalis to the east, shares a short border with Lacerta to the west; the three-letter abbreviation for the constellation, as adopted by the International Astronomical Union in 1922, is'Cas'. The official constellation boundaries, as set by Eugène Delporte in 1930, are defined by a polygon of 30 segments. In the equatorial coordinate system, the right ascension coordinates of these borders lie between 00h 27m 03s and 23h 41m 06s, while the decl
Tasmania is an island state of Australia. It is located 240 km to the south of the Australian mainland, separated by Bass Strait; the state encompasses the main island of Tasmania, the 26th-largest island in the world, the surrounding 334 islands. The state has a population of around 526,700 as of March 2018. Just over forty percent of the population resides in the Greater Hobart precinct, which forms the metropolitan area of the state capital and largest city, Hobart. Tasmania's area is 68,401 km2, of which the main island covers 64,519 km2, it is promoted as a natural state, protected areas of Tasmania cover about 42% of its land area, which includes national parks and World Heritage Sites. Tasmania was the founding place of the first environmental political party in the world; the island is believed to have been occupied by indigenous peoples for 30,000 years before British colonisation. It is thought Aboriginal Tasmanians were separated from the mainland Aboriginal groups about 10,000 years ago when the sea rose to form Bass Strait.
The Aboriginal population is estimated to have been between 3,000 and 7,000 at the time of colonisation, but was wiped out within 30 years by a combination of violent guerrilla conflict with settlers known as the "Black War", intertribal conflict, from the late 1820s, the spread of infectious diseases to which they had no immunity. The conflict, which peaked between 1825 and 1831, led to more than three years of martial law, cost the lives of 1,100 Aboriginals and settlers; the island was permanently settled by Europeans in 1803 as a penal settlement of the British Empire to prevent claims to the land by the First French Empire during the Napoleonic Wars. The island was part of the Colony of New South Wales but became a separate, self-governing colony under the name Van Diemen's Land in 1825. 75,000 convicts were sent to Van Diemen's Land before transportation ceased in 1853. In 1854 the present Constitution of Tasmania was passed, the following year the colony received permission to change its name to Tasmania.
In 1901 it became a state through the process of the Federation of Australia. The state is named after Dutch explorer Abel Tasman, who made the first reported European sighting of the island on 24 November 1642. Tasman named the island Anthony van Diemen's Land after his sponsor Anthony van Diemen, the Governor of the Dutch East Indies; the name was shortened to Van Diemen's Land by the British. It was renamed Tasmania in honour of its first European discoverer on 1 January 1856. Tasmania was sometimes referred to as "Dervon," as mentioned in the Jerilderie Letter written by the notorious Australian bushranger Ned Kelly in 1879; the colloquial expression for the state is "Tassie". Tasmania is colloquially shortened to "Tas," when used in business names and website addresses. TAS is the Australia Post abbreviation for the state; the reconstructed Palawa kani language name for Tasmania is Lutriwita. The island was adjoined to the mainland of Australia until the end of the last glacial period about 10,000 years ago.
Much of the island is composed of Jurassic dolerite intrusions through other rock types, sometimes forming large columnar joints. Tasmania has the world's largest areas of dolerite, with many distinctive mountains and cliffs formed from this rock type; the central plateau and the southeast portions of the island are dolerites. Mount Wellington above Hobart is a good example. In the southern midlands as far south as Hobart, the dolerite is underlaid by sandstone and similar sedimentary stones. In the southwest, Precambrian quartzites were formed from ancient sea sediments and form strikingly sharp ridges and ranges, such as Federation Peak or Frenchmans Cap. In the northeast and east, continental granites can be seen, such as at Freycinet, similar to coastal granites on mainland Australia. In the northwest and west, mineral-rich volcanic rock can be seen at Mount Read near Rosebery, or at Mount Lyell near Queenstown. Present in the south and northwest is limestone with caves; the quartzite and dolerite areas in the higher mountains show evidence of glaciation, much of Australia's glaciated landscape is found on the Central Plateau and the Southwest.
Cradle Mountain, another dolerite peak, for example, was a nunatak. The combination of these different rock types contributes to scenery, distinct from any other region of the world. In the far southwest corner of the state, the geology is wholly quartzite, which gives the mountains the false impression of having snow-capped peaks year round. Evidence indicates the presence of Aborigines in Tasmania about 42,000 years ago. Rising sea levels cut Tasmania off from mainland Australia about 10,000 years ago and by the time of European contact, the Aboriginal people in Tasmania had nine major nations or ethnic groups. At the time of the British occupation and colonisation in 1803, the indigenous population was estimated at between 3,000 and 10,000. Historian Lyndall Ryan's analysis of population studies led her to conclude that there were about 7,000 spread throughout the island's nine nations. J. B. Plomley and Rhys Jones, settled on a figure of 3,000 to 4,000, they engaged in fire-stick farming, hunted game including kangaroo and wallabies, caught seals, mutton-birds and fish and lived as nine separate "nations" on the island, which they knew as "Trouwunna".
The first reported sighting of Tasmania by a European was on 24 November 1642 by Dutch explorer Abel Tasman, who landed at today's Blackman Bay. More than a century in 1772, a French expedition le