1.
Alvan Clark
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Alvan Clark, born in Ashfield, Massachusetts, the descendant of a Cape Cod whaling family of English ancestry, was an American astronomer and telescope maker. He was a painter and engraver, and at the age of 40 became involved in telescope making. One of Clarks sons, Alvan Graham Clark, discovered the dim companion of Sirius and his other son was George Bassett Clark, both sons were partners in the firm. The crater Clark on the Moon is jointly named for him and his son, Alvan Graham Clark, Alvan Clark & Sons List of astronomical instrument makers List of largest optical refracting telescopes Portraits by Clark Alvan Clark, Astronomy, Biographies. Deborah Jean Warner & Robert B, Alvan Clark & Sons, Artists in Optics. Boston Daily Evening Transcript,19 August 1887, new-England Historical and Genealogical Register 43, 52-58. Alvan Clark & Sons, Artists in Optics, national Gallery of Art has works by Clark
2.
Flagstaff, Arizona
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Flagstaff is a city in northern Arizona, in the southwestern United States. In 2015, the estimated population was 70,320. Flagstaffs combined metropolitan area has an population of 139,097. It is the county seat of Coconino County, the city is named after a ponderosa pine flagpole made by a scouting party from Boston to celebrate the United States Centennial on July 4,1876. Flagstaff lies near the edge of the Colorado Plateau, along the western side of the largest contiguous Ponderosa Pine forest in the continental United States. Flagstaff is located adjacent to Mount Elden, just south of the San Francisco Peaks, humphreys Peak, the highest point in Arizona at 12,633 feet, is located about 10 miles north of Flagstaff in Kachina Peaks Wilderness. Flagstaffs early economy was based on the lumber, railroad, Flagstaff has a strong tourism sector, due to its proximity to Grand Canyon National Park, Oak Creek Canyon, the Arizona Snowbowl, Meteor Crater, and historic Route 66. The city is also a center for medical device manufacturing, since Flagstaff is home to W. L. Gore, there exist several stories and legends regarding the origin of the citys name. It is said that, because of the flag that was raised, the first permanent settlement was in 1876, when Thomas F. McMillan built a cabin at the base of Mars Hill on the west side of town. During the 1880s, Flagstaff began to grow, opening its first post office, the early economy was based on timber, sheep, and cattle. By 1886, Flagstaff was the largest city on the line between Albuquerque and the west coast of the United States. A circa 1900 diary entry by journalist Sharlot Hall described the houses in the city at the time as a third rate mining camp, with unkempt air, in 1894, Massachusetts astronomer Percival Lowell hired A. E. Douglass to scout an ideal site for a new observatory. Douglass, impressed by Flagstaffs elevation, named it as a location for the now famous Lowell Observatory, saying, other things being equal. Two years later, the specially designed 24-inch Clark telescope that Lowell had ordered was installed, in 1930, Pluto was discovered using one of the observatorys telescopes. During the Apollo program in the 1960s, the Clark Telescope was used to map the moon for the lunar expeditions, in homage to the citys importance in the field of astronomy, asteroid 2118 Flagstaff is named for the city, and 6582 Flagsymphony for the Flagstaff Symphony Orchestra. The Northern Arizona Normal School was established in 1899, renamed Northern Arizona University in 1966, Flagstaffs cultural history received a significant boost on April 11,1899, when the Flagstaff Symphony made its concert debut at Babbitts Opera House. The orchestra continues today as the Flagstaff Symphony Orchestra, with its venue at the Ardrey Auditorium on the campus of Northern Arizona University. The city grew rapidly, primarily attributable to its location along the east–west transcontinental railroad line in the United States, in the 1880s, the railroads purchased land in the west from the federal government, which was then sold to individuals to help finance the railroad projects
3.
Geographic coordinate system
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A geographic coordinate system is a coordinate system used in geography that enables every location on Earth to be specified by a set of numbers, letters or symbols. The coordinates are chosen such that one of the numbers represents a vertical position. A common choice of coordinates is latitude, longitude and elevation, to specify a location on a two-dimensional map requires a map projection. The invention of a coordinate system is generally credited to Eratosthenes of Cyrene. Ptolemy credited him with the adoption of longitude and latitude. Ptolemys 2nd-century Geography used the prime meridian but measured latitude from the equator instead. Mathematical cartography resumed in Europe following Maximus Planudes recovery of Ptolemys text a little before 1300, in 1884, the United States hosted the International Meridian Conference, attended by representatives from twenty-five nations. Twenty-two of them agreed to adopt the longitude of the Royal Observatory in Greenwich, the Dominican Republic voted against the motion, while France and Brazil abstained. France adopted Greenwich Mean Time in place of local determinations by the Paris Observatory in 1911, the latitude of a point on Earths surface is the angle between the equatorial plane and the straight line that passes through that point and through the center of the Earth. Lines joining points of the same latitude trace circles on the surface of Earth called parallels, as they are parallel to the equator, the north pole is 90° N, the south pole is 90° S. The 0° parallel of latitude is designated the equator, the plane of all geographic coordinate systems. The equator divides the globe into Northern and Southern Hemispheres, the longitude of a point on Earths surface is the angle east or west of a reference meridian to another meridian that passes through that point. All meridians are halves of great ellipses, which converge at the north and south poles, the prime meridian determines the proper Eastern and Western Hemispheres, although maps often divide these hemispheres further west in order to keep the Old World on a single side. The antipodal meridian of Greenwich is both 180°W and 180°E, the combination of these two components specifies the position of any location on the surface of Earth, without consideration of altitude or depth. The grid formed by lines of latitude and longitude is known as a graticule, the origin/zero point of this system is located in the Gulf of Guinea about 625 km south of Tema, Ghana. To completely specify a location of a feature on, in, or above Earth. Earth is not a sphere, but a shape approximating a biaxial ellipsoid. It is nearly spherical, but has an equatorial bulge making the radius at the equator about 0. 3% larger than the radius measured through the poles, the shorter axis approximately coincides with the axis of rotation
4.
Discovery Channel Telescope
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The Discovery Channel Telescope is a 4.3 m aperture telescope built by Lowell Observatory and The Discovery Channel. DCT was built at a dark sky site in the Coconino National Forest near Happy Jack, Happy Jack is located at an elevation of 2,360 m and is approximately 65 km south-south-east of Flagstaff. The project was initially a partnership between Discovery Communications and Lowell Observatory, the research partnerships have been extended to include Boston University, The University of Maryland, The University of Toledo, and Northern Arizona University. In its initial implementation, the telescope will cost approximately US$53 million, the telescope will significantly augment Lowell Observatory’s observational capability and enable pioneering studies in a number of important research areas. Final construction of the telescope was completed by February 2012 and first light images were taken in April 2012, the DCT is designed to support a variety of optical configurations. The phase one configuration will be ideal for high-resolution imaging and spectroscopy both at visible and the near-infrared wavelengths, the telescope is designed to allow a very large,0. 2-degree field of view in its prime focus implementation – a possible future upgrade. The DCT was designed by Alan Dodson, Lowell Observatory and Discovery Communications formed a partnership to build the Discovery Channel Telescope in February 2003. The primary mirror blank was completed by Corning in late 2005, construction of the 26-meter-tall, 19-meter-diameter telescope enclosure and an auxiliary support building began in mid-September 2005. Final figuring and polishing of the mirror, which weighs about 3,000 kg, was completed by the University of Arizona’s College of Optical Sciences and this process took about three years. The mirror was delivered to the site in June 2010, subsequently aluminized, the telescope saw first light in 2012 and it was fully operational that year. It was only expected to be a 4.2 m, the telescope will initially be applied to a wide and evolving range of research topics
5.
Cassegrain reflector
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The Cassegrain reflector is a combination of a primary concave mirror and a secondary convex mirror, often used in optical telescopes and radio antennas. Alternatively, as in radio telescopes, the final focus may be in front of the primary. In an asymmetrical Cassegrain, the mirror may be tilted to avoid obscuration of the primary or to avoid the need for a hole in the primary mirror, the classic Cassegrain configuration uses a parabolic reflector as the primary while the secondary mirror is hyperbolic. Modern variants often have a primary for increased performance, or the primary and/or secondary are spherical or elliptical for ease of manufacturing. The Cassegrain reflector is named after a published reflecting telescope design that appeared in the April 25,1672 Journal des sçavans which has been attributed to Laurent Cassegrain. Similar designs using convex secondaries have been found in the Bonaventura Cavalieris 1632 writings describing burning mirrors, james Gregorys 1662 attempts to create a reflecting telescope included a Cassegrain configuration, judging by a convex secondary mirror found among his experiments. The Cassegrain design is used in catadioptric systems. The Classic Cassegrain has a primary mirror, and a hyperbolic secondary mirror that reflects the light back down through a hole in the primary. Folding the optics makes this a compact design, on smaller telescopes, and camera lenses, the secondary is often mounted on an optically flat, optically clear glass plate that closes the telescope tube. This support eliminates the diffraction effects caused by a straight-vaned support spider. The closed tube stays clean, and the primary is protected and it makes use of the special properties of parabolic and hyperbolic reflectors. A concave parabolic reflector will reflect all incoming light rays parallel to its axis of symmetry to a single point, a convex hyperbolic reflector has two foci and will reflect all light rays directed at one of its two foci towards its other focus. The parabolic mirror reflects parallel light rays entering the telescope to its focus, the hyperbolic mirror then reflects those light rays to its other focus, where the image is observed. The Ritchey-Chrétien is a specialized Cassegrain reflector which has two hyperbolic mirrors and it is free of coma and spherical aberration at a flat focal plane, making it well suited for wide field and photographic observations. It was invented by George Willis Ritchey and Henri Chrétien in the early 1910s and this design is very common in large professional research telescopes, including the Hubble Space Telescope, Keck Telescopes and VLT telescope, it is also found in high-grade amateur telescopes. Ingalls, the astronomy editor at the time. It uses a concave primary mirror and a convex spherical secondary. While this system is easier to polish than a classic Cassegrain or Ritchey-Chretien system, because this is less noticeable at longer focal ratios, Dall-Kirkhams are seldom faster than f/15
6.
Reflecting telescope
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A reflecting telescope is an optical telescope which uses a single or combination of curved mirrors that reflect light and form an image. The reflecting telescope was invented in the 17th century as an alternative to the telescope which. Although reflecting telescopes produce other types of aberrations, it is a design that allows for very large diameter objectives. Almost all of the telescopes used in astronomy research are reflectors. Reflecting telescopes come in many variations and may employ extra optical elements to improve image quality or place the image in a mechanically advantageous position. Since reflecting telescopes use mirrors, the design is referred to as a catoptric telescope. The idea that curved mirrors behave like lenses dates back at least to Alhazens 11th century treatise on optics, the potential advantages of using parabolic mirrors, primarily reduction of spherical aberration with no chromatic aberration, led to many proposed designs for reflecting telescopes. The most notable being James Gregory, who published a design for a ‘reflecting’ telescope in 1663. It would be ten years, before the experimental scientist Robert Hooke was able to build this type of telescope, Isaac Newton has been generally credited with building the first reflecting telescope in 1668. It used a spherically ground metal primary mirror and a diagonal mirror in an optical configuration that has come to be known as the Newtonian telescope. A curved primary mirror is the reflector telescopes basic optical element that creates an image at the focal plane, the distance from the mirror to the focal plane is called the focal length. The primary mirror in most modern telescopes is composed of a glass cylinder whose front surface has been ground to a spherical or parabolic shape. A thin layer of aluminum is deposited onto the mirror. Some telescopes use primary mirrors which are made differently, molten glass is rotated to make its surface paraboloidal, and is kept rotating while it cools and solidifies. The resulting mirror shape approximates a desired paraboloid shape that requires grinding and polishing to reach the exact figure needed. Reflecting telescopes, just like any other system, do not produce perfect images. The use of mirrors avoids chromatic aberration but they produce other types of aberrations, to avoid this problem most reflecting telescopes use parabolic shaped mirrors, a shape that can focus all the light to a common focus. Field curvature - The best image plane is in general curved and it is sometimes corrected by a field flattening lens
7.
Lowell Observatory Near-Earth-Object Search
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Lowell Observatory Near-Earth-Object Search was a project designed to discover asteroids and comets that orbit near the Earth. The project, funded by NASA, was directed by Dr. Ted Bowell of Lowell Observatory in Flagstaff, the LONEOS project began in 1993 and ran until the end of February 2008. LONEOS, in its configuration, used a 0. 6-meter f/1.8 Schmidt telescope, acquired from Ohio Wesleyan University in 1990. This combination of instruments provided a field of view of 2.88 by 2.88 degrees and it had a maximum nightly scan area of about 1,000 square degrees. The instrument could cover the entire accessible dark sky in about a month, the CCD has detected asteroids as faint as visual magnitude 19.8 but its typical limiting visual magnitude was 19.3. The instrument is located at Lowell Observatorys dark sky site, Anderson Mesa Station, near Flagstaff, Arizona, two were used for frame reductions, one for telescope pointing control and one for camera control. The camera control software had scripting capability and could control all the other computers, asteroids were found by obtaining four pictures of the same region of sky, each frame temporally separated by 15 to 30 minutes. The set of four frames were then submitted to reduction software which located all star-like sources on the frame, the observer visually examined all asteroid detections that had motion different from a typical main-belt asteroid. Human examination was required because most putative NEO detections were not real, all asteroid positions were converted to equatorial coordinates. Various USNO star catalogs were used for this conversion until 2007, then the Sloan Digital Sky Survey catalog was used, along with supplemental information from the Carlsberg Catalog and the 2MASS catalog. Asteroid brightness was converted to standard visual magnitude and these data, along with the time of the observations, were sent to the Minor Planet Center from which they were distributed to the scientific community. Potential near-Earth objects were handled expeditiously so that other observers could locate the asteroid on the same night, telescope operation was automated to the extent that the survey could be run all night without observer intervention. However, the telescope was operated in the automatic mode because an observer was required to reduce data promptly. During the period of LONEOS operation, several other NASA funded NEO searches were underway and these projects include LINEAR, CSS, Spacewatch, and NEAT. Amateur observers made a significant contribution during this time with independent NEO discoveries, the table below lists the number of discoveries made by LONEOS each year of operation. Asteroids thought to be larger than one kilometer in diameter were used as benchmarks in assessing survey completeness, hence, some table elements have two numbers separated by a slash. The second number represents the number of larger than one kilometer. The column labeled Asteroid Observations is the number of sent to the MPC
8.
Catadioptric system
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A catadioptric optical system is one where refraction and reflection are combined in an optical system, usually via lenses and curved mirrors. Catadioptric combinations are used in focusing systems such as lights, headlamps, early lighthouse focusing systems, optical telescopes, microscopes. Other optical systems use lenses and mirrors are also referred to as catadioptric such as surveillance catadioptric sensors. Catadioptric combinations have been used in many optical systems. In the 1820s, Augustin-Jean Fresnel developed several catadioptric lighthouse reflectors, léon Foucault developed a catadioptric microscope in 1859 to counteract aberrations of using a lens to image objects at high power. In 1876 a French engineer, A. Mangin, invented what has come to be called the Mangin mirror, the two surfaces of the reflector have different radii to correct the aberration of the spherical mirror. Light passes through the glass twice, making the system act like a triplet lens. Mangin mirrors were used in searchlights, where they produced a true parallel beam. Catadioptric telescopes are optical telescopes that combine specifically shaped mirrors and lenses to form an image and their designs can have simple all-spherical surfaces and can take advantage of a folded optical path that reduces the mass of the telescope, making them easier to manufacture. Catadioptric dialytes are the earliest type of catadioptric telescope and they consist of a single-element refractor objective combined with a silver-backed negative lens. The first of these was the Hamiltonian telescope patented by W. F. Hamilton in 1814, there are several telescope designs that take advantage of placing one or more full-diameter lenses in front of a spherical primary mirror. Some of these designs have been adapted to create compact, long-focal-length catadioptric cassegrains, the Schmidt corrector, the first full-diameter corrector plate, was used in Bernhard Schmidts 1931 Schmidt camera. The relatively thin and lightweight corrector allows Schmidt cameras to be constructed in diameters up to 1.3 m, the design has lent itself to many Schmidt variants. Popular sub-types Schmidt–Cassegrain telescopes are one of the most popular commercial designs on the amateur astronomical market, the design replaces the Schmidt Camera film holder with a Cassegrain secondary mirror, making a folded optical path with a long focal length and a narrow field of view. Wartime secrecy kept these inventors from knowing about each others designs, albert Bouwers built a prototype meniscus telescope in August 1940 and patented it in February 1941. It used a spherically concentric meniscus and was suitable as a monochromatic astronomical camera. In a later design he added a cemented doublet to correct chromatic aberration, Dmitri Maksutov built a prototype for a similar type of meniscus telescope, the Maksutov telescope, in October 1941 and patented it in November of that same year. His design corrected spherical and chromatic aberrations by placing a weak negative-shaped meniscus corrector closer to the primary mirror, popular sub-types Maksutov–Cassegrain telescopes are the most commonly seen design that uses a meniscus corrector, a variant of the Maksutov telescope
9.
Alvan Clark & Sons
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Alvan Clark & Sons was an American maker of optics that became famous for crafting lenses for some of the largest refracting telescopes of the 19th and early 20th centuries. Founded in 1846 in Cambridgeport, Massachusetts, by Alvan Clark, five times, the firm built the largest refracting telescopes in the world. The Clark firm gained worldwide fame and distribution, wrote one author on astronomy in 1899, the 18. 5-inch Dearborn telescope was commissioned in 1856 by the University of Mississippi. The outbreak of war prevented them from ever taking ownership. As a result, it was being tested in Cambridgeport when Alvan Graham observed Sirius B in 1862, in 1873 they built the 26-inch objective lens for the refractor at the United States Naval Observatory. The company also built a number of instruments, which are still highly prized among collectors. The companys assets were acquired by the Sprague-Hathaway Manufacturing Company in 1933, most of Clarks equipment was disposed of as scrap during World War II, and Sprague-Hathaway itself was liquidated in 1958. Alvan Clark & Sons Telescopes Chabot Space & Science Center, Oakland, California Charles Sumner Tainter Deborah Jean Warner, ariail, Alvan Clark & Sons, artists in optics Richmond, VA. Willmann-Bell, in association with National Museum of American History, Smithsonian Institution,1995,298 p. ISBN 0-943396-46-8 Timothy Ferris, Seeing in the Dark Simon & Schuster 2002, 117p
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