1.
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
2.
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
3.
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
4.
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
5.
Refracting telescope
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A refracting telescope is a type of optical telescope that uses a lens as its objective to form an image. The refracting telescope design was used in spy glasses and astronomical telescopes but is also used for long focus camera lenses. A refractors magnification is calculated by dividing the length of the objective lens by that of the eyepiece. Refractors were the earliest type of optical telescope, Galileo Galilei, happening to be in Venice in about the month of May 1609, heard of the invention and constructed a version of his own. Galileo then communicated the details of his invention to the public, all refracting telescopes use the same principles. The objective in a refracting telescope refracts or bends light and this refraction causes parallel light rays to converge at a focal point, while those not parallel converge upon a focal plane. The telescope converts a bundle of rays to make an angle α. The ratio β/α is called the angular magnification and it equals the ratio between the retinal image sizes obtained with and without the telescope. Refracting telescopes can come in different configurations to correct for image orientation. Because the image was formed by the bending of light, or refraction, the design Galileo Galilei used in 1609 is commonly called a Galilean telescope. It used a convergent objective lens and a divergent eyepiece lens, a Galilean telescope, because the design has no intermediary focus, results in a non-inverted and upright image. Galileo’s best telescope magnified objects about 30 times, because of flaws in its design, such as the shape of the lens and the narrow field of view, the images were blurry and distorted. Despite these flaws, the telescope was still enough for Galileo to explore the sky. The Galilean telescope could view the phases of Venus, and was able to see craters on the Moon, parallel rays of light from a distant object would be brought to a focus in the focal plane of the objective lens. The eyepiece lens intercepts these rays and renders them parallel once more, non-parallel rays of light from the object traveling at an angle α1 to the optical axis travel at a larger angle after they passed through the eyepiece. This leads to an increase in the apparent angular size and is responsible for the perceived magnification, the final image is a virtual image, located at infinity and is the same way up as the object. The Keplerian telescope, invented by Johannes Kepler in 1611, is an improvement on Galileos design and it uses a convex lens as the eyepiece instead of Galileos concave one. The advantage of this arrangement is that the rays of light emerging from the eyepiece are converging and this allows for a much wider field of view and greater eye relief, but the image for the viewer is inverted
6.
Astrograph
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An astrograph is a telescope designed for the sole purpose of astrophotography. Astrographs are usually used in wide field surveys of the sky as well as detection of objects such as asteroids, meteors. Most research telescopes in this class are refractors, although there are many reflecting designs such as the Ritchey-Chrétien, the main parameters of an Astrograph are the diameter and f-ratio of the objective, which determine the field of view and image scale on the photographic plate or CCD detector. The objective of an astrograph is usually not very large, on the order of 20 to 50 cm, the shape of the focal plane is often designed to work in conjunction with a specific shaped photographic plate or CCD detector. The objective is designed to produce a large, flat. They may even be designed to certain wavelengths of light to match the type of film they are designed to use. Wide-angle astrographs with short f-ratios are used for photographing a huge area of sky, astrographs with higher f-ratios are used in more precise measurements. Many observatories of the world are equipped with the so-called normal astrographs with an aperture of around 13 inches, the purpose of a normal astrograph is to create images where the scale of the image at the focal plane is a standard of approximately 60 arcsecs/mm. Astrographs used in astrometry record images that are used to map the positions of objects over a large area of the sky. These maps are published in catalogs to be used in further study or to serve as reference points for deep-space imaging. Astrographs used for stellar classification sometimes consist of two telescopes on the same mount. Each sky field can be photographed in two colors. Each telescope may have individually designed non-achromatic objectives to focus the desired wavelength of light which is paired with the respective color-sensitive photographic plate. In other cases a single telescope is used to make two exposures of the part of the sky with different filters and color sensitive film used on each exposure. Two-color photography lets astronomers measure the color, as well as the brightness, knowing the color type and magnitudes lets astronomers determine the distance of a star. Sky fields that are photographed twice, decades apart in time, by taking two exposures of the same section of the sky days or weeks apart, it is possible to find objects such as asteroids, meteors, comets, variable stars, novae, and even unknown planets. Sometimes objects can even be found in one exposure since a fast moving object appear as a line in a long exposure. One well-known case of a used in a discovery is Clyde Tombaugh’s discovery of the dwarf planet Pluto in 1930
7.
Astronomical interferometer
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The advantage of this technique is that it can theoretically produce images with the angular resolution of a huge telescope with an aperture equal to the separation between the component telescopes. The main drawback is that it does not collect as much light as the complete instruments mirror, thus it is mainly useful for fine resolution of more luminous astronomical objects, such as close binary stars. Another drawback is that the angular size of a detectable emission source is limited by the minimum gap between detectors in the collector array. Interferometry is most widely used in astronomy, in which signals from separate radio telescopes are combined. A mathematical signal processing technique called aperture synthesis is used to combine the signals to create high-resolution images. Practical infrared and optical astronomical interferometers have only recently been developed, at optical wavelengths, aperture synthesis allows the atmospheric seeing resolution limit to be overcome, allowing the angular resolution to reach the diffraction limit of the optics. Astronomical interferometers can produce higher resolution images than any other type of telescope. At radio wavelengths, image resolutions of a few micro-arcseconds have been obtained, one simple layout of an astronomical interferometer is a parabolic arrangement of mirror pieces, giving a partially complete reflecting telescope but with a sparse or dilute aperture. Instead, most existing arrays use a geometry, and Labeyries hypertelescope will use a spherical geometry. One of the first uses of optical interferometry was applied by the Michelson stellar interferometer on the Mount Wilson Observatorys reflector telescope to measure the diameters of stars, the red giant star Betelgeuse was the first to have its diameter determined in this way on December 13,1920. In the 1940s radio interferometry was used to perform the first high resolution radio astronomy observations, optical/infrared interferometry was extended to measurements using separated telescopes by Johnson, Betz and Townes in the infrared and by Labeyrie in the visible. Similar techniques have now been applied at other astronomical telescope arrays, including the Keck Interferometer, software packages such as BSMEM or MIRA are used to convert the measured visibility amplitudes and closure phases into astronomical images. If completed, the MRO Interferometer with up to ten movable telescopes will produce among the first higher fidelity images from a long baseline interferometer, astronomical interferometry is principally conducted using Michelson interferometers. The principal operational interferometric observatories which use this type of instrumentation include VLTI, NPOI, engineers at the European Southern Observatory ESO designed the Very Large Telescope VLT so that it can also be used as an interferometer. Along with the four 8. 2-metre unit telescopes, four mobile 1. 8-metre auxiliary telescopes were included in the overall VLT concept to form the Very Large Telescope Interferometer. The ATs can move between 30 different stations, and at present, the telescopes can form groups of two or three for interferometry, when using interferometry, a complex system of mirrors brings the light from the different telescopes to the astronomical instruments where it is combined and processed. This is technically demanding as the light paths must be equal to within 1/1000 mm over distances of a few hundred metres. For the Unit Telescopes, this gives an equivalent mirror diameter of up to 130 metres, and this is up to 25 times better than the resolution of a single VLT unit telescope
8.
United States Naval Observatory
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The USNO operates the Master Clock, which provides precise time to the GPS satellite constellation run by the United States Air Force. The USNO performs radio VLBI-based positions of quasars with numerous global collaborators, aside from its scientific mission, a house located within the Naval Observatory complex serves as the official residence of the Vice President of the United States. President John Quincy Adams, who in 1825 signed the bill for the creation of an observatory just before leaving presidential office, had intended for it to be called the National Observatory. The names National Observatory and Naval Observatory were both used for 10 years, until a ruling was passed to use the latter. Adams had made protracted efforts to bring astronomy to a level at that time. He spent many nights at the observatory, watching and charting the stars, established by the order of the United States Secretary of the Navy John Branch on 6 December 1830 as the Depot of Charts and Instruments, the Observatory rose from humble beginnings. Placed under the command of Lieutenant Louis M. Goldsborough, with an budget of $330, its primary function was the restoration, repair. It was made into an observatory in 1842 via a federal law. Lieutenant James Melville Gilliss was put in charge of obtaining the instruments needed, lt. Gilliss visited the principal observatories of Europe with the mission to purchase telescopes and scientific devices and books. The observatorys primary mission was to care for the United States Navys marine chronometers, charts and it calibrated ships chronometers by timing the transit of stars across the meridian. These facilities were listed on the National Register of Historic Places in 2017, the first superintendent was Navy Commander Matthew Fontaine Maury. Maury had the worlds first vulcanized time ball, created to his specifications by Charles Goodyear for the U. S. Observatory and it was the first time ball in the United States, being placed into service in 1845, and the 12th in the world. Maury kept accurate time by the stars and planets, the time ball was dropped every day except Sunday precisely at the astronomically defined moment of Mean Solar Noon, enabling all ships and civilians to know the exact time. Time was also sold to the railroads and was used in conjunction with railroad chronometers to schedule American rail transport, early in the 20th century, the Arlington Time Signal broadcast this service to wireless receivers. In 1849 the Nautical Almanac Office was established in Cambridge, Massachusetts as a separate organization and it was moved to Washington, D. C. in 1866, colocating with the U. S. Naval Observatory in 1893. On September 20,1894, the NAO became a branch of USNO, the astronomical measurements taken of the transit of Venus by a number of countries since 1639 resulted in a progressively more accurate definition of the AU. Relying heavily on methods, the naval observers returned 350 photographic plates in 1874. This calculated distance was a significant improvement over several previous estimates, the telescope used for the discovery of the Moons of Mars was the 26-inch refractor, then located at Foggy Bottom
9.
United States Naval Observatory Flagstaff Station
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The United States Naval Observatory Flagstaff Station, is an astronomical observatory near Flagstaff, Arizona, USA. It is the national dark-sky observing facility under the United States Naval Observatory, NOFS and USNO combine as the Celestial Reference Frame manager for the U. S. Secretary of Defense. NOFS science supports every aspect of astronomy to some level, providing national support. Work at NOFS covers the gamut of astrometry and astrophysics in order to facilitate its production of accurate/precise astronomical catalogs, multiple observations of each object may themselves take weeks, months or years, by themselves. The United States Naval Observatory, Flagstaff Station celebrated its 50th anniversary of the move there from Washington, dr. John Hall, Director of the Naval Observatorys Equatorial Division from 1947, founded NOFS. Dr. Art Hoag became its first director in 1955, both later were to become directors of nearby Lowell Observatory. NOFS remains active in supporting regional dark skies, both to support its national mission, and to promote and protect a national resource legacy for generations of humans to come. Indeed, despite a history, NOFS has a rich heritage which is derived from its parent organization, USNO. Navy since it saw first light in 1964 and this status will change when the NPOI four 1. 8-meter telescopes see their own first light in the near future. KSAR rides in the arms of a fork mount. The telescope is used in both the spectrum, and in the near infrared, the latter using a sub-30-Kelvin, helium-refrigerated, InSb camera. In 1978, the 1. 55-m telescope was used to discover the moon of dwarf planet Pluto, the Charon discovery led to mass calculations which ultimately revealed how tiny Pluto was, and eventually caused the IAU to reclassify Pluto as a dwarf planet. The 1. 55-meter telescope was used to observe and track NASAs Deep Impact Spacecraft, as it navigated to a successful inter-planetary impact with the celebrated Comet 9p/Tempel. The 61 dome is located on NOFS grounds, with support. The large vacuum coating chamber facility is located in this complex. A dielectric coating capability has also been demonstrated, large optics and telescope components can be moved about NOFS using its suite of cranes, lifts, cargo elevators and specialized carts. The KSAR Telescopes 60-foot diameter steel dome is large for the telescopes aperture. It uses a very wide 2-shutter, vertical slit. 6-meters, by using fast, however, the 61-inch telescope remains unique in its ability to operationally conduct both very high-accuracy relative astrometry to the milliarcsecond level, and close-separation, PSF photometry
10.
United States Naval Research Laboratory
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A few of the laboratorys current specialties include plasma physics, space physics, materials science, and tactical electronic warfare. NRL is one of the first US Government scientific R&D laboratories, having opened in 1923 at the instigation of Thomas Edison, NRLs research expenditures are approximately $1.1 billion per year. The Naval Research Laboratory conducts a variety of basic and scientific research. It has a history of scientific breakthroughs and technological achievements dating back to its foundation in 1923. In many instances the contributions to military technology are declassified decades after those technologies have become widely adopted. In 2011, NRL researchers published 1,398 unclassified scientific & technical articles, book chapters, in 2008, the NRL was ranked #3 among all U. S. institutions holding nanotechnology-related patents, behind IBM and the University of California. The laboratory houses a range of R&D facilities. The most recent additions include the NRL Nanoscience Institutes 5000sqft Class 100 nanofabrication cleanroom and quiet measurement labs, the Naval Research Laboratory has been a crucial piece of the United States space program. Project Vanguard, the first American satellite program, tasked NRL with the design, construction and launch of an artificial satellite, Vanguard I, designed and built at NRL, was the first solar-powered satellite. As of 2013, Vanguard I is still in orbit, making it the longest-lived man-made satellite, Vanguard II was the first satellite to observe the Earths cloud cover and therefore the first meteorological satellite. NRL pioneered the study of the sun Ultraviolet and X-Ray spectrum, along with Project Vanguard, NRL also designed the first satellite tracking system, Minitrack, which became the prototype for future satellite tracking networks. NRLs recently declassified Galactic Radiation and Background I was the first U. S. intelligence satellite, NRLs spacecraft development program continues today with the TacSat-4 experimental tactical reconnaissance & communication satellite. In addition to design, NRL also designs and operates research instruments, such as the Large Angle and Spectrometric Coronagraph Experiment aboard the Solar. NASAs Gamma-ray Large Area Space Telescope was tested at NRL spacecraft testing facilities, NRL scientists have most recently contributed leading research to the study of novas and gamma ray bursts. Modern mechanical fracture mechanics were pioneered at NRL and were applied to solve fracture problems in Navy vessels, commercial aircraft. That knowledge is in use today in applications ranging from design of nuclear reactors to aircraft, submarines. NRLs GaAs inventions were licensed by Rockwell, Westinghouse, Texas Instruments, high-purity GaAs is also used for high-efficiency solar cells like those aboard NASAs Spirit and Opportunity rovers currently on Mars. Fundamental aspects of technology were developed at NRL, including the radar absorption mechanisms in ferrite-containing materials
11.
National Register of Historic Places
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The National Register of Historic Places is the United States federal governments official list of districts, sites, buildings, structures, and objects deemed worthy of preservation. The passage of the National Historic Preservation Act in 1966 established the National Register, of the more than one million properties on the National Register,80,000 are listed individually. The remainder are contributing resources within historic districts, each year approximately 30,000 properties are added to the National Register as part of districts or by individual listings. For most of its history the National Register has been administered by the National Park Service and its goals are to help property owners and interest groups, such as the National Trust for Historic Preservation, coordinate, identify, and protect historic sites in the United States. While National Register listings are mostly symbolic, their recognition of significance provides some financial incentive to owners of listed properties, protection of the property is not guaranteed. During the nomination process, the property is evaluated in terms of the four criteria for inclusion on the National Register of Historic Places, the application of those criteria has been the subject of criticism by academics of history and preservation, as well as the public and politicians. Occasionally, historic sites outside the proper, but associated with the United States are also listed. Properties can be nominated in a variety of forms, including individual properties, historic districts, the Register categorizes general listings into one of five types of properties, district, site, structure, building, or object. National Register Historic Districts are defined geographical areas consisting of contributing and non-contributing properties, some properties are added automatically to the National Register when they become administered by the National Park Service. These include National Historic Landmarks, National Historic Sites, National Historical Parks, National Military Parks/Battlefields, National Memorials, on October 15,1966, the Historic Preservation Act created the National Register of Historic Places and the corresponding State Historic Preservation Offices. Initially, the National Register consisted of the National Historic Landmarks designated before the Registers creation, approval of the act, which was amended in 1980 and 1992, represented the first time the United States had a broad-based historic preservation policy. To administer the newly created National Register of Historic Places, the National Park Service of the U. S. Department of the Interior, hartzog, Jr. established an administrative division named the Office of Archeology and Historic Preservation. Hartzog charged OAHP with creating the National Register program mandated by the 1966 law, ernest Connally was the Offices first director. Within OAHP new divisions were created to deal with the National Register, the first official Keeper of the Register was William J. Murtagh, an architectural historian. During the Registers earliest years in the late 1960s and early 1970s, organization was lax and SHPOs were small, understaffed, and underfunded. A few years later in 1979, the NPS history programs affiliated with both the U. S. National Parks system and the National Register were categorized formally into two Assistant Directorates. Established were the Assistant Directorate for Archeology and Historic Preservation and the Assistant Directorate for Park Historic Preservation, from 1978 until 1981, the main agency for the National Register was the Heritage Conservation and Recreation Service of the United States Department of the Interior. In February 1983, the two assistant directorates were merged to promote efficiency and recognize the interdependency of their programs, jerry L. Rogers was selected to direct this newly merged associate directorate
12.
Astronomy
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Astronomy is a natural science that studies celestial objects and phenomena. It applies mathematics, physics, and chemistry, in an effort to explain the origin of those objects and phenomena and their evolution. Objects of interest include planets, moons, stars, galaxies, and comets, while the phenomena include supernovae explosions, gamma ray bursts, more generally, all astronomical phenomena that originate outside Earths atmosphere are within the purview of astronomy. A related but distinct subject, physical cosmology, is concerned with the study of the Universe as a whole, Astronomy is the oldest of the natural sciences. The early civilizations in recorded history, such as the Babylonians, Greeks, Indians, Egyptians, Nubians, Iranians, Chinese, during the 20th century, the field of professional astronomy split into observational and theoretical branches. Observational astronomy is focused on acquiring data from observations of astronomical objects, theoretical astronomy is oriented toward the development of computer or analytical models to describe astronomical objects and phenomena. The two fields complement each other, with theoretical astronomy seeking to explain the results and observations being used to confirm theoretical results. Astronomy is one of the few sciences where amateurs can play an active role, especially in the discovery. Amateur astronomers have made and contributed to many important astronomical discoveries, Astronomy means law of the stars. Astronomy should not be confused with astrology, the system which claims that human affairs are correlated with the positions of celestial objects. Although the two share a common origin, they are now entirely distinct. Generally, either the term astronomy or astrophysics may be used to refer to this subject, however, since most modern astronomical research deals with subjects related to physics, modern astronomy could actually be called astrophysics. Few fields, such as astrometry, are purely astronomy rather than also astrophysics, some titles of the leading scientific journals in this field includeThe Astronomical Journal, The Astrophysical Journal and Astronomy and Astrophysics. In early times, astronomy only comprised the observation and predictions of the motions of objects visible to the naked eye, in some locations, early cultures assembled massive artifacts that possibly had some astronomical purpose. Before tools such as the telescope were invented, early study of the stars was conducted using the naked eye, most of early astronomy actually consisted of mapping the positions of the stars and planets, a science now referred to as astrometry. From these observations, early ideas about the motions of the planets were formed, and the nature of the Sun, Moon, the Earth was believed to be the center of the Universe with the Sun, the Moon and the stars rotating around it. This is known as the model of the Universe, or the Ptolemaic system. The Babylonians discovered that lunar eclipses recurred in a cycle known as a saros
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