An observatory is a location used for observing terrestrial or celestial events. Astronomy, climatology/meteorology, geophysical and volcanology are examples of disciplines for which observatories have been constructed. Observatories were as simple as containing an astronomical sextant or Stonehenge. Astronomical observatories are divided into four categories: space-based, ground-based, underground-based. Ground-based observatories, located on the surface of Earth, are used to make observations in the radio and visible light portions of the electromagnetic spectrum. Most optical telescopes are housed within a dome or similar structure, to protect the delicate instruments from the elements. Telescope domes have a slit or other opening in the roof that can be opened during observing, closed when the telescope is not in use. In most cases, the entire upper portion of the telescope dome can be rotated to allow the instrument to observe different sections of the night sky. Radio telescopes do not have domes.
For optical telescopes, most ground-based observatories are located far from major centers of population, to avoid the effects of light pollution. The ideal locations for modern observatories are sites that have dark skies, a large percentage of clear nights per year, dry air, are at high elevations. At high elevations, the Earth's atmosphere is thinner, thereby minimizing the effects of atmospheric turbulence and resulting in better astronomical "seeing". Sites that meet the above criteria for modern observatories include the southwestern United States, Canary Islands, the Andes, high mountains in Mexico such as Sierra Negra. A newly emerging site which should be added to this list is Mount Gargash. With an elevation of 3600 m above sea level, it is the home to the Iranian National Observatory and its 3.4m INO340 telescope. Major optical observatories include Mauna Kea Observatory and Kitt Peak National Observatory in the US, Roque de los Muchachos Observatory and Calar Alto Observatory in Spain, Paranal Observatory in Chile.
Specific research study performed in 2009 shows that the best possible location for ground-based observatory on Earth is Ridge A — a place in the central part of Eastern Antarctica. This location provides the least atmospheric disturbances and best visibility. Beginning in 1930s, radio telescopes have been built for use in the field of radio astronomy to observe the Universe in the radio portion of the electromagnetic spectrum; such an instrument, or collection of instruments, with supporting facilities such as control centres, visitor housing, data reduction centers, and/or maintenance facilities are called radio observatories. Radio observatories are located far from major population centers to avoid electromagnetic interference from radio, TV, other EMI emitting devices, but unlike optical observatories, radio observatories can be placed in valleys for further EMI shielding; some of the world's major radio observatories include the Socorro, in New Mexico, United States, Jodrell Bank in the UK, Arecibo in Puerto Rico, Parkes in New South Wales and Chajnantor in Chile.
Since the mid-20th century, a number of astronomical observatories have been constructed at high altitudes, above 4,000–5,000 m. The largest and most notable of these is the Mauna Kea Observatory, located near the summit of a 4,205 m volcano in Hawaiʻi; the Chacaltaya Astrophysical Observatory in Bolivia, at 5,230 m, was the world's highest permanent astronomical observatory from the time of its construction during the 1940s until 2009. It has now been surpassed by the new University of Tokyo Atacama Observatory, an optical-infrared telescope on a remote 5,640 m mountaintop in the Atacama Desert of Chile; the oldest proto-observatories, in the sense of a private observation post, Wurdi Youang, Australia Zorats Karer, Armenia Loughcrew, Ireland Newgrange, Ireland Stonehenge, Great Britain Quito Astronomical Observatory, located 12 minutes south of the Equator in Quito, Ecuador. Chankillo, Peru El Caracol, Mexico Abu Simbel, Egypt Kokino, Republic of Macedonia Observatory at Rhodes, Greece Goseck circle, Germany Ujjain, India Arkaim, Russia Cheomseongdae, South Korea Angkor Wat, CambodiaThe oldest true observatories, in the sense of a specialized research institute, include: 825 AD: Al-Shammisiyyah observatory, Iraq 869: Mahodayapuram Observatory, India 1259: Maragheh observatory, Iran 1276: Gaocheng Astronomical Observatory, China 1420: Ulugh Beg Observatory, Uzbekistan 1442: Beijing Ancient Observatory, China 1577: Constantinople Observatory of Taqi ad-Din, Turkey 1580: Uraniborg, Denmark 1581: Stjerneborg, Denmark 1642: Panzano Observatory, Italy 1642: Round Tower, Denmark 1633: Leiden Observatory, Netherlands 1667: Paris Observatory, France 1675: Royal Greenwich Observatory, England 1695: Sukharev Tower, Russia 1711: Berlin Observatory, Germany 1724: Jantar Mantar, India 1753: Stockholm Observatory, Sweden 1753: Vilnius University Observatory, Lithuania 1753: Navy Royal Institute and Observatory, Spain 1759: Trieste Observatory, Italy 1757: Macfarlane Observatory, Scotland 1759: Turin Observatory, Italy 1764: Brera Astronomical Observatory, Italy 1765: Mohr Observatory, Indonesia 1774: Vatican Observatory, Vatican 1785: Dunsink Observatory, Ireland 1786: Madras Observatory, India 1789: Armagh Observatory, Northern Ireland 1790: Real Observatorio de Madrid, Spain, 1803: National Astronomical Observatory, Bogotá, Colombia.
1811: Tartu Old Observatory, Estonia 1812: Astronomical Observatory of Capodimonte, Italy 1830/1842: Depot of Charts & Instruments
An astrograph is a telescope designed for the sole purpose of astrophotography. Astrographs are used in wide field astronomical surveys of the sky and for detection of objects such as asteroids and comets. Most research telescopes in this class are refractors, although there are many reflecting designs such as the Ritchey-Chrétien and catadioptrics such as the Schmidt camera; 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 not large, on the order of 20 to 50 cm; the shape of the focal plane is designed to work in conjunction with a specific shaped photographic plate or CCD detector. The objective is designed to produce a large and distortion-less image at the focal plane, they may be designed to focus 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 and a focal length of 11 feet; the purpose of a "normal astrograph" is to create images where the scale of the image at the focal plane is a standard of 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 identical 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, paired with the respective color-sensitive photographic plate. In other cases a single telescope is used to make two exposures of the same 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, of each star imaged. Colors tell the star's "temperature”. Knowing the color type and magnitudes lets astronomers determine the distance of a star. Sky fields that are photographed twice, decades apart in time, will reveal a nearby star's proper motion when measured against the background of distant stars or galaxies. By taking two exposures of the same section of the sky days or weeks apart, it is possible to find objects such as asteroids, comets, variable stars and unknown planets. By comparing the pair of images, using a device such as a blink comparator, astronomers are able to find objects that moved or changed brightness between the two exposures or appear in one image only, as in the case of a nova or meteor. Sometimes objects can be found in one exposure since a fast moving object will appear as a "line" in a long exposure. One well-known case of an astrograph used in a discovery is Clyde Tombaugh’s discovery of the dwarf planet Pluto in 1930.
Tombaugh was given the job of hunting for a suspected "9th planet" to be achieved by systematically photographing the area of the sky around the ecliptic. Tombaugh used Lowell Observatory's 13-inch, f/5.3 refractor astrograph, which recorded images on 14-by-17-inch glass plates. In the amateur astronomy field many types of commercial and amateur built telescopes are designed for astrophotography and labeled "astrographs". Optical designs of amateur astrographs vary but include apochromatic refractors, variations of Cassegrain reflectors, Newtonian reflectors. Most optical designs do not produce large and well-corrected imaging fields and therefore require some type of optical correction by way of field flatteners or coma correctors. Amateur astrographs have purpose-built focusers, are constructed of thermally stable materials like carbon fiber, are put on heavy duty mounts to facilitate accurate tracking of deep sky objects for long periods of time. BOOTES List of telescope types The Double Astrograph of the Yale Southern Observatory The Carnegie Double Astrograph Pluto Imaging Challenge: Images Construction of the Tycho Reference Catalogue - 2 Source Catalogues
The Nasmyth telescope called Nasmyth–Cassegrain or Cassegrain–Nasmyth, is a reflecting telescope developed by James Nasmyth. It is a modified form of a Cassegrain telescope, with light reflected sideways before reaching the primary mirror again; as in the Cassegrain telescope, the light falls on a concave primary mirror is reflected towards a convex secondary mirror. A comparatively small tertiary flat mirror reflects the light to one of the sides of the telescope; this flat mirror is placed on the altitude axis, so that the beam exits through a hole in the middle of the altitude bearing. This means the eyepiece or instrument does not need to move up and down with the telescope as the tertiary mirror's angle with the main telescope axis is adjustable as a function of the telescope's pointing and the star's elevation above the horizon; this has significant advantages for spectrographs and other heavy instruments used at research observatories. Most modern research telescopes can be configured into a Nasmyth telescope.
The twin 10-meter telescopes at W. M. Keck Observatory in Hawaii and the 8.2-meter Subaru Telescope sited next to them support an array of specialized instruments on Nasmyth platforms, with a similar design being used for the future Thirty Meter Telescope. The 2.4-meter Automated Planet Finder telescope at Lick Observatory supports the use of two Nasmyth foci. The Sierra Nevada Observatory in Spain has two Nasmyth telescopes, including a 1.5-meter diameter aperture one. The SOFIA airborne telescope uses this design. Cassegrain antenna List of telescope types List of astronomical observatories Nasmyth Telescope, Murdin, P. Encyclopedia of Astronomy and Astrophysics Instruments on the two Nasmyth foci of each the VLT unit telescopes
A Ritchey–Chrétien telescope is a specialized variant of the Cassegrain telescope that has a hyperbolic primary mirror and a hyperbolic secondary mirror designed to eliminate off-axis optical errors. The RCT has a wider field of view free of optical errors compared to a more traditional reflecting telescope configuration. Since the mid 20th century, a majority of large professional research telescopes have been Ritchey–Chrétien configurations; the Ritchey–Chrétien telescope was invented in the early 1910s by American astronomer George Willis Ritchey and French astronomer Henri Chrétien. Ritchey constructed the first successful RCT, which had a diameter aperture of 60 cm in 1927; the second RCT was a 102 cm instrument constructed by Ritchey for the United States Naval Observatory. The basic Ritchey–Chrétien two-surface design is free of third-order coma and spherical aberration, although it does suffer from fifth-order coma, severe large-angle astigmatism, comparatively severe field curvature.
The remaining aberrations of the basic design may be improved with the addition of smaller optical elements near the focal plane. When focused midway between the sagittal and tangential focusing planes, stars are imaged as circles, making the RCT well suited for wide field and photographic observations; as with the other Cassegrain-configuration reflectors, the RCT has a short optical tube assembly and compact design for a given focal length. The RCT offers good off-axis optical performance, but the Ritchey–Chrétien configuration is most found on high-performance professional telescopes. A telescope with only one curved mirror, such as a Newtonian telescope, will always have aberrations. If the mirror is spherical, it will suffer from spherical aberration. If the mirror is made parabolic, to correct the spherical aberration it must suffer from coma and astigmatism. With two non-spherical mirrors, such as the Ritchey–Chrétien telescope, coma can be eliminated as well; this allows a larger useful field of view.
However, such designs still suffer from astigmatism. This too can be cancelled by including a third curved optical element; when this element is a mirror, the result is a three-mirror anastigmat. Alternatively, a Ritchey-Chrétien may use one or several low-power lenses in front of the focal plane as a field-corrector to correct astigmatism and flatten the focal surface, as for example the SDSS telescope and the VISTA telescope. In practice, each of these designs may include any number of flat fold mirrors, used to bend the optical path into more convenient configurations. In a Ritchey-Chrétien design, as in most Cassegrain systems, the secondary mirror blocks a central portion of the aperture; this ring-shaped entrance aperture reduces a portion of the modulation transfer function over a range of low spatial frequencies, compared to a full-aperture design such as a refractor. This MTF notch has the effect of lowering image contrast. In addition the support for the secondary may introduce diffraction spikes in images.
The radii of curvature of the primary and secondary mirrors in a two-mirror Cassegrain configuration are R 1 = − 2 D F F − B and R 2 = − 2 D B F − B − D where F is the effective focal length of the system, B is the back focal length, D is the distance between the two mirrors. If, instead of B and D, the known quantities are the focal length of the primary mirror, f 1, the distance to the focus behind the primary mirror, b D = f 1 / and B = D + b. For a Ritchey–Chrétien system, the conic constants K 1 and K 2 of the two mirrors are chosen so as to eliminate third-order spherical aberration and coma.
The Hoher List is a stratovolcano, 549.1 m above sea level, near the town of Daun in the Eifel region. The hill is in the county of Vulkaneifel in the German state of Rhineland-Palatinate; the Hoher List lies in the Volcanic Eifel, part of the Eifel Mountains, in the Volcanic Eifel Nature Park. It is located about 4.5 km as the crow flies south of the town of Daun southwest of Schalkenmehren by the Schalkenmehrener Maar. On the summit of this sparsely wooded domed hill stands the Hoher List Observatory and, on its densely forested southwestern spur at an elevation of 540.1 m is the castle of Altburg. The L 64 state road, a section of the Eifel-Ardennes Road, runs past the summit of the Hoher List, linking Schalkenmehren to the north with Brockscheid to the south
University of Bonn
The University of Bonn is a public research university located in Bonn, Germany. It was founded in its present form as the Rhein University on 18 October 1818 by Frederick William III, as the linear successor of the Kurkölnische Akademie Bonn, founded in 1777; the University of Bonn offers a large number of undergraduate and graduate programs in a range of subjects and has 544 professors and 32,500 students. Its library holds more than five million volumes; as of August 2018, among its notable alumni and researchers are 10 Nobel Laureates, 4 Fields Medalists, twelve Gottfried Wilhelm Leibniz Prize winners as well as August Kekulé, Friedrich Nietzsche, Karl Marx, Heinrich Heine, Prince Albert, Pope Benedict XVI, Frederick III, Max Ernst, Konrad Adenauer, Joseph Schumpeter. The university's forerunner was the Kurkölnische Akademie Bonn, founded in 1777 by Maximilian Frederick of Königsegg-Rothenfels, the prince-elector of Cologne. In the spirit of the Enlightenment the new academy was nonsectarian.
The academy had schools for theology, law and general studies. In 1784 Emperor Joseph II granted the academy the right to award academic degrees, turning the academy into a university; the academy was closed in 1798 after the left bank of the Rhine was occupied by France during the French Revolutionary Wars. The Rhineland became a part of Prussia in 1815 as a result of the Congress of Vienna. King Frederick William III of Prussia thereafter decreed the establishment of a new university in the new province on 18 October 1818. At this time there was no university in the Rhineland, as all three universities that existed until the end of the 18th century were closed as a result of the French occupation; the Kurkölnische Akademie Bonn was one of these three universities. The other two were the Roman Catholic University of Cologne and the Protestant University of Duisburg; the new Rhein University was founded on 18 October 1818 by Frederick William III. It was the sixth Prussian University, founded after the universities in Greifswald, Berlin, Königsberg and Breslau.
The new university was shared between the two Christian denominations. This was one of the reasons why Bonn, with its tradition of a nonsectarian university, was chosen over Cologne and Duisburg. Apart from a school of Roman Catholic theology and a school of Protestant theology, the university had schools for medicine and philosophy. 35 professors and eight adjunct professors were teaching in Bonn. The university constitution was adopted in 1827. In the spirit of Wilhelm von Humboldt the constitution emphasized the autonomy of the university and the unity of teaching and research. Similar to the University of Berlin, founded in 1810, the new constitution made the University of Bonn a modern research university. Only one year after the inception of the Rhein University the dramatist August von Kotzebue was murdered by Karl Ludwig Sand, a student at the University of Jena; the Carlsbad Decrees, introduced on 20 September 1819 led to a general crackdown on universities, the dissolution of the Burschenschaften and the introduction of censorship laws.
One victim was the author and poet Ernst Moritz Arndt, freshly appointed university professor in Bonn, was banned from teaching. Only after the death of Frederick William III in 1840 was he reinstated in his professorship. Another consequence of the Carlsbad Decrees was the refusal by Frederick William III to confer the chain of office, the official seal and an official name to the new university; the Rhein University was thus nameless until 1840, when the new King of Prussia, Frederick William IV gave it the official name Rheinische Friedrich-Wilhelms-Universität. Despite these problems, the university attracted famous scholars and students. At the end of the 19th century the university was known as the Prinzenuniversität, as many of the sons of the king of Prussia studied here. In 1900, the university had 68 chairs, 23 adjunct chairs, two honorary professors, 57 Privatdozenten and six lecturers. Since 1896, women were allowed to attend classes as guest auditors at universities in Prussia. In 1908 the University of Bonn became coeducational.
The growth of the university came to a halt with World War I. Financial and economic problems in Germany in the aftermath of the war resulted in reduced government funding for the university; the University of Bonn responded by trying to find industrial sponsors. In 1930 the university adopted a new constitution. For the first time students were allowed to participate in the self-governing university administration. To that effect the student council Astag was founded in the same year. Members of the student council were elected in a secret ballot. After the Nazi takeover of power in 1933, the Gleichschaltung transformed the university into a Nazi educational institution. According to the Führerprinzip the autonomous and self-governening administration of the university was replaced by a hierarchy of leaders resembling the military, with the university president being subordinate to the ministry of education. Jewish professors and students and political opponents were ostracized and expelled from the university