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Hvar Observatory
The Hvar Observatory, part of the Geodetic school of the University of Zagreb, is an astronomical research observatory located above the city of Hvar (the observatory's dome is between 173 and 245 meters above sea level). Opened in 1972, research at the observatory focuses on solar physics; the photometry of stars, especially variable class Be stars; and star clusters and galaxies. A double telescope is used for solar observation: one telescope observes the photosphere (opening diameter 217 mm, focal length 2450 mm) and the other observes the chromosphere (opening diameter 130 mm, focal length 1950 mm) with a narrowband spectral filter. For stellar observation, a Cassegrain reflector with an opening diameter of 65 cm is used. Since 1997 a shared Austro-Croatian telescope is also used for stellar observation, which has a mirror diameter of 1 m and is also a Cassegrain reflector. The observatory is located above the city of Hvar on the southwest portion of Hvar island, on a steep hill ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
University Of Zagreb
The University of Zagreb ( hr, Sveučilište u Zagrebu, ; la, Universitas Studiorum Zagrabiensis) is the largest Croatian university and the oldest continuously operating university in the area covering Central Europe south of Vienna and all of Southeastern Europe. The University of Zagreb and the University North are the only public universities operating in Northern and Central Croatia. The history of the University began on September 23, 1669, when the Holy Roman Emperor Leopold I issued a decree granting the establishment of the ''Jesuit Academy of the Royal Free City of Zagreb''. The decree was accepted at the Council of the Croatian Kingdom on November 3, 1671. The Academy was run by the Jesuits for more than a century until the order was dissolved by Pope Clement XIV in 1773. In 1776, Empress Maria Theresa issued a decree founding the ''Royal Academy of Science'' which succeeded the previous Jesuit Academy. Bishop Josip Juraj Strossmayer proposed the founding of a Univ ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hvar (city)
Hvar (Chakavian: ''For'', el, Φάρος, Pharos, la, Pharus and , it, Lesina) is a town and port on the island of Hvar, part of Split-Dalmatia County, Croatia. The municipality has a population of 4,251 (2011) while the town itself is inhabited by 3,771 people, making it the largest settlement on the island of Hvar. It is situated on a bay in the south coast of the island, opposite from the other nearby towns of Stari Grad, Croatia, Stari Grad and Jelsa, Croatia, Jelsa. The town of Hvar has a long and distinguished history as center for trade and culture in the Adriatic. A commune, part of the Venetian Empire during the 13th to 18th centuries, it was an important naval base with a strong fortress above, encircling the town walls and protecting the port. Cultural life thrived as prosperity grew, and Hvar is the site of one of the oldest surviving theatres in Europe, opened in 1612. The seven-hundred-year-old walls still survive, as do many of the noble houses and public buildi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Photometry (astronomy)
Photometry, from Greek '' photo-'' ("light") and '' -metry'' ("measure"), is a technique used in astronomy that is concerned with measuring the flux or intensity of light radiated by astronomical objects. This light is measured through a telescope using a photometer, often made using electronic devices such as a CCD photometer or a photoelectric photometer that converts light into an electric current by the photoelectric effect. When calibrated against standard stars (or other light sources) of known intensity and colour, photometers can measure the brightness or apparent magnitude of celestial objects. The methods used to perform photometry depend on the wavelength region under study. At its most basic, photometry is conducted by gathering light and passing it through specialized photometric optical bandpass filters, and then capturing and recording the light energy with a photosensitive instrument. Standard sets of passbands (called a photometric system) are defined to allow a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Variable Star
A variable star is a star whose brightness as seen from Earth (its apparent magnitude) changes with time. This variation may be caused by a change in emitted light or by something partly blocking the light, so variable stars are classified as either: * Intrinsic variables, whose luminosity actually changes; for example, because the star periodically swells and shrinks. * Extrinsic variables, whose apparent changes in brightness are due to changes in the amount of their light that can reach Earth; for example, because the star has an orbiting companion that sometimes eclipses it. Many, possibly most, stars have at least some variation in luminosity: the energy output of the Sun, for example, varies by about 0.1% over an 11-year solar cycle. Discovery An ancient Egyptian calendar of lucky and unlucky days composed some 3,200 years ago may be the oldest preserved historical document of the discovery of a variable star, the eclipsing binary Algol. Of the modern astronomers, th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Be Star
Be stars are a heterogeneous set of stars with B spectral types and emission lines. A narrower definition, sometimes referred to as ''classical Be stars'', is a non-supergiant B star whose spectrum has, or had at some time, one or more Balmer emission lines. Definition and classification Many stars have B-type spectra and show hydrogen emission lines, including many supergiants, Herbig Ae/Be stars, mass-transferring binary systems, and B stars. It is preferred to restrict usage of the term Be star to non-supergiant stars showing one or more Balmer series lines in emission. These are sometimes referred to as classical Be stars. The emission lines may be present only at certain times. Although the Be type spectrum is most strongly produced in class B stars, it is also detected in O and A shell stars, and these are sometimes included under the "Be star" banner. Be stars are primarily considered to be main sequence stars, but a number of subgiants and giant stars are also inc ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Photosphere
The photosphere is a star's outer shell from which light is radiated. The term itself is derived from Ancient Greek roots, φῶς, φωτός/''phos, photos'' meaning "light" and σφαῖρα/''sphaira'' meaning "sphere", in reference to it being a spherical surface that is perceived to emit light. It extends into a star's surface until the plasma becomes opaque, equivalent to an optical depth of approximately , or equivalently, a depth from which 50% of light will escape without being scattered. A photosphere is the deepest region of a luminous object, usually a star, that is transparent to photons of certain wavelengths. Temperature The surface of a star is defined to have a temperature given by the effective temperature in the Stefan–Boltzmann law. Stars, except neutron stars, have no solid or liquid surface. Therefore, the photosphere is typically used to describe the Sun's or another star's visual surface. Composition of the Sun The Sun is composed primarily of ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Chromosphere
A chromosphere ("sphere of color") is the second layer of a star's atmosphere, located above the photosphere and below the solar transition region and corona. The term usually refers to the Sun's chromosphere, but not exclusively. In the Sun's atmosphere, the chromosphere is roughly in height, or slightly more than 1% of the Sun's radius at maximum thickness. It possesses a homogeneous layer at the boundary with the photosphere. Hair-like jets of plasma, called spicules, rise from this homogeneous region and through the chromosphere, extending up to into the corona above. The chromosphere has a characteristic red color due to electromagnetic emissions in the ''H''α spectral line. Information about the chromosphere is primarily obtained by analysis of its emitted electromagnetic radiation. Chromospheres have also been observed on stars other than the Sun. On large stars, chromospheres sometimes make up a significant proportion of the entire star. For example, the chro ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cassegrain Reflector
The Cassegrain reflector is a combination of a primary concave mirror and a secondary convex mirror, often used in optical telescopes and radio antennas, the main characteristic being that the optical path folds back onto itself, relative to the optical system's primary mirror entrance aperture. This design puts the focal point at a convenient location behind the primary mirror and the convex secondary adds a telephoto effect creating a much longer focal length in a mechanically short system. In a symmetrical Cassegrain both mirrors are aligned about the optical axis, and the primary mirror usually contains a hole in the center, thus permitting the light to reach an eyepiece, a camera, or an image sensor. Alternatively, as in many radio telescopes, the final focus may be in front of the primary. In an asymmetrical Cassegrain, the mirror(s) may be tilted to avoid obscuration of the primary or to avoid the need for a hole in the primary mirror (or both). The classic Cassegrain ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hvar
Hvar (; Chakavian: ''Hvor'' or ''For'', el, Φάρος, Pharos, la, Pharia, it, Lesina) is a Croatian island in the Adriatic Sea, located off the Dalmatian coast, lying between the islands of Brač, Vis and Korčula. Approximately long, with a high east–west ridge of Mesozoic limestone and dolomite, the island of Hvar is unusual in the area for having a large fertile coastal plain, and fresh water springs. Its hillsides are covered in pine forests, with vineyards, olive groves, fruit orchards and lavender fields in the agricultural areas. The climate is characterized by mild winters, and warm summers with many hours of sunshine. The island has 10,739 residents according to the 2021 census, making it the 4th most populated of the Croatian islands. Hvar's location at the centre of the Adriatic sailing routes has long made this island an important base for commanding trade up and down the Adriatic, across to Italy and throughout the wider Mediterranean. It has been inhabite ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Napoleonic Wars
The Napoleonic Wars (1803–1815) were a series of major global conflicts pitting the French Empire and its allies, led by Napoleon I, against a fluctuating array of European states formed into various coalitions. It produced a period of French domination over most of continental Europe. The wars stemmed from the unresolved disputes associated with the French Revolution and the French Revolutionary Wars consisting of the War of the First Coalition (1792–1797) and the War of the Second Coalition (1798–1802). The Napoleonic Wars are often described as five conflicts, each termed after the coalition that fought Napoleon: the Third Coalition (1803–1806), the Fourth (1806–1807), the Fifth (1809), the Sixth (1813–1814), and the Seventh (1815) plus the Peninsular War (1807–1814) and the French invasion of Russia (1812). Napoleon, upon ascending to First Consul of France in 1799, had inherited a republic in chaos; he subsequently created a state with stable financ ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Socialist Republic Of Croatia
The Socialist Republic of Croatia ( sh-Latn-Cyrl, separator=" / ", Socijalistička Republika Hrvatska, Социјалистичка Република Хрватска), or SR Croatia, was a constituent republic and federated state of the Socialist Federal Republic of Yugoslavia. By its constitution, modern-day Croatia is its direct continuation. Along with five other Yugoslav republics, it was formed during World War II and became a socialist republic after the war. It had four full official names during its 48-year existence ( see below). By territory and population, it was the second largest republic in Yugoslavia, after the Socialist Republic of Serbia. In 1990, the government dismantled the single-party system of government – installed by the League of Communists – and adopted a multi-party democracy. The newly elected government of Franjo Tuđman moved the republic towards independence, formally seceding from Yugoslavia in 1991 and thereby contributing to its disso ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Czechoslovak Academy Of Sciences
The Czechoslovak Academy of Sciences (Czech: ''Československá akademie věd'', Slovak: ''Česko-slovenská akadémia vied'') was established in 1953 to be the scientific center for Czechoslovakia. It was succeeded by the Czech Academy of Sciences (''Akademie věd České republiky'') and Slovak Academy of Sciences (''Slovenská akadémia vied'') in 1992. History The Royal Czech Society of Sciences, which encompassed both the humanities and the natural sciences, was established in the Czech Crown lands in 1784. After the Communist regime came to power in Czechoslovakia in 1948, all scientific, non-university institutions and learned societies were dissolved and, in their place, the Czechoslovak Academy of Sciences was founded by Act No. 52/1952. It comprised both a complex of research institutes and a learned society. The Slovak Academy of Sciences, established in 1942 and re-established in 1953, was a formal part of the Czechoslovak Academy of Sciences from 1960 to 1992. During ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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