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- Observational_astronomy abstract "Observational astronomy is a division of the astronomical science that is concerned with recording data, in contrast with theoretical astrophysics, which is mainly concerned with finding out the measurable implications of physical models. It is the practice of observing celestial objects by using telescopes and other astronomical apparatus.As a science, the study of astronomy is somewhat hindered in that direct experiments with the properties of the distant universe are not possible. However, this is partly compensated by the fact that astronomers have a vast number of visible examples of stellar phenomena that can be examined. This allows for observational data to be plotted on graphs, and general trends recorded. Nearby examples of specific phenomena, such as variable stars, can then be used to infer the behavior of more distant representatives. Those distant yardsticks can then be employed to measure other phenomena in that neighborhood, including the distance to a galaxy.Galileo Galilei turned a telescope to the heavens and recorded what he saw. Since that time, observational astronomy has made steady advances with each improvement in telescope technology.A traditional division of observational astronomy is given by the region of the electromagnetic spectrum observed: Optical astronomy is the part of astronomy that uses optical components (mirrors, lenses and solid-state detectors) to observe light from near infrared to near ultraviolet wavelengths. Visible-light astronomy (using wavelengths that can be detected with the eyes, about 400 - 700 nm) falls in the middle of this range. Infrared astronomy deals with the detection and analysis of infrared radiation (this typically refers to wavelengths longer than the detection limit of silicon solid-state detectors, about 1 μm wavelength). The most common tool is the reflecting telescope but with a detector sensitive to infrared wavelengths. Space telescopes are used at certain wavelengths where the atmosphere is opaque, or to eliminate noise (thermal radiation from the atmosphere). Radio astronomy detects radiation of millimetre to decametre wavelength. The receivers are similar to those used in radio broadcast transmission but much more sensitive. See also Radio telescopes. High-energy astronomy includes X-ray astronomy, gamma-ray astronomy, and extreme UV astronomy.In addition to using electromagnetic radiation, modern astrophysicists can also make observations using neutrinos, cosmic rays or gravitational waves. Observing a source using multiple methods is known as multi-messenger astronomy.Optical and radio astronomy can be performed with ground-based observatories, because the atmosphere is relatively transparent at the wavelengths being detected. Observatories are usually located at high altitudes so as to minimise the absorption and distortion caused by the Earth's atmosphere. Some wavelengths of infrared light are heavily absorbed by water vapor, so many infrared observatories are located in dry places at high altitude, or in space.The atmosphere is opaque at the wavelengths used by X-ray astronomy, gamma-ray astronomy, UV astronomy and (except for a few wavelength \"windows\") far infrared astronomy, so observations must be carried out mostly from balloons or space observatories. Powerful gamma rays can, however be detected by the large air showers they produce, and the study of cosmic rays is a rapidly expanding branch of astronomy.For much of the history of observational astronomy, almost all observation was performed in the visual spectrum with optical telescopes. While the Earth's atmosphere is relatively transparent in this portion of the electromagnetic spectrum, most telescope work is still dependent on seeing conditions and air transparency, and is generally restricted to the night time. The seeing conditions depend on the turbulence and thermal variations in the air. Locations that are frequently cloudy or suffer from atmospheric turbulence limit the resolution of observations. Likewise the presence of the full Moon can brighten up the sky with scattered light, hindering observation of faint objects.For observation purposes, the optimal location for an optical telescope is undoubtedly in outer space. There the telescope can make observations without being affected by the atmosphere. However, at present it remains costly to lift telescopes into orbit. Thus the next best locations are certain mountain peaks that have a high number of cloudless days and generally possess good atmospheric conditions (with good seeing conditions). The peaks of the islands of Mauna Kea, Hawaii and La Palma possess these properties, as to a lesser extent do inland sites such as Llano de Chajnantor, Paranal, Cerro Tololo and La Silla in Chile. These observatory locations have attracted an assemblage of powerful telescopes, totalling many billion US dollars of investment.The darkness of the night sky is an important factor in optical astronomy. With the size of cities and human populated areas ever expanding, the amount of artificial light at night has also increased. These artificial lights produce a diffuse background illumination that makes observation of faint astronomical features very difficult without special filters. In a few locations such as the state of Arizona and in the United Kingdom, this has led to campaigns for the reduction of light pollution. The use of hoods around street lights not only improves the amount of light directed toward the ground, but also helps reduce the light directed toward the sky.Atmospheric effects (astronomical seeing) can severely hinder the resolution of a telescope. Without some means of correcting for the blurring effect of the shifting atmosphere, telescopes larger than about 15–20 cm in aperture can not achieve their theoretical resolution at visible wavelengths. As a result, the primary benefit of using very large telescopes has been the improved light-gathering capability, allowing very faint magnitudes to be observed. However the resolution handicap has begun to be overcome by adaptive optics, speckle imaging and interferometric imaging, as well as the use of space telescopes.Astronomers have a number of observational tools that they can use to make measurements of the heavens. For objects that are relatively close to the Sun and Earth, direct and very precise position measurements can be made against a more distant (and thereby nearly stationary) background. Early observations of this nature were used to develop very precise orbital models of the various planets, and to determine their respective masses and gravitational perturbations. Such measurements led to the discovery of the planets Uranus, Neptune, and (indirectly) Pluto. They also resulted in an erroneous assumption of a fictional planet Vulcan within the orbit of Mercury (but the explanation of the precession of Mercury's orbit by Einstein is considered one of the triumphs of his general relativity theory).".
- Observational_astronomy thumbnail Mayall_Telescope.jpg?width=300.
- Observational_astronomy wikiPageExternalLink lot.astro.utoronto.ca.
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- Observational_astronomy wikiPageWikiLink Active_galactic_nucleus.
- Observational_astronomy wikiPageWikiLink Adaptive_optics.
- Observational_astronomy wikiPageWikiLink Air_shower_(physics).
- Observational_astronomy wikiPageWikiLink Albert_Einstein.
- Observational_astronomy wikiPageWikiLink Altazimuth_mount.
- Observational_astronomy wikiPageWikiLink Aperture.
- Observational_astronomy wikiPageWikiLink Aperture_synthesis.
- Observational_astronomy wikiPageWikiLink Apparent_magnitude.
- Observational_astronomy wikiPageWikiLink Arizona.
- Observational_astronomy wikiPageWikiLink Asteroid.
- Observational_astronomy wikiPageWikiLink Astrometry.
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- Observational_astronomy wikiPageWikiLink Astronomy.
- Observational_astronomy wikiPageWikiLink Astrophotography.
- Observational_astronomy wikiPageWikiLink Astrophysics.
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- Observational_astronomy wikiPageWikiLink Balloon.
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- Observational_astronomy wikiPageWikiLink Cepheid_variable.
- Observational_astronomy wikiPageWikiLink Cerro_Tololo_Inter-American_Observatory.
- Observational_astronomy wikiPageWikiLink Charge-coupled_device.
- Observational_astronomy wikiPageWikiLink Chile.
- Observational_astronomy wikiPageWikiLink Color_index.
- Observational_astronomy wikiPageWikiLink Comet.
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- Observational_astronomy wikiPageWikiLink Cosmic_microwave_background.
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- Observational_astronomy wikiPageWikiLink Far-infrared_astronomy.
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- Observational_astronomy wikiPageWikiLink Galaxy.
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- Observational_astronomy wikiPageWikiLink General_relativity.
- Observational_astronomy wikiPageWikiLink Geology.
- Observational_astronomy wikiPageWikiLink Globular_cluster.
- Observational_astronomy wikiPageWikiLink Gravitational_wave.
- Observational_astronomy wikiPageWikiLink HALCA.
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- Observational_astronomy wikiPageWikiLink Helium.
- Observational_astronomy wikiPageWikiLink High-energy_astronomy.
- Observational_astronomy wikiPageWikiLink Hubble_Space_Telescope.
- Observational_astronomy wikiPageWikiLink Hydrogen.
- Observational_astronomy wikiPageWikiLink Infrared.
- Observational_astronomy wikiPageWikiLink Infrared_astronomy.
- Observational_astronomy wikiPageWikiLink Interferometry.
- Observational_astronomy wikiPageWikiLink La_Silla_Observatory.
- Observational_astronomy wikiPageWikiLink Light.
- Observational_astronomy wikiPageWikiLink Light_pollution.
- Observational_astronomy wikiPageWikiLink List_of_astronomical_observatories.
- Observational_astronomy wikiPageWikiLink List_of_radio_telescopes.
- Observational_astronomy wikiPageWikiLink Llano_de_Chajnantor_Observatory.
- Observational_astronomy wikiPageWikiLink Luminosity.
- Observational_astronomy wikiPageWikiLink Lunar_observation.
- Observational_astronomy wikiPageWikiLink Maksutov_telescope.
- Observational_astronomy wikiPageWikiLink Mauna_Kea_Observatories.
- Observational_astronomy wikiPageWikiLink Mercury_(planet).
- Observational_astronomy wikiPageWikiLink Meteorology.
- Observational_astronomy wikiPageWikiLink Micrometer.
- Observational_astronomy wikiPageWikiLink Moon.
- Observational_astronomy wikiPageWikiLink Neptune.
- Observational_astronomy wikiPageWikiLink Neutrino.
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- Observational_astronomy wikiPageWikiLink Neutron_star.
- Observational_astronomy wikiPageWikiLink Newtonian_telescope.
- Observational_astronomy wikiPageWikiLink Nuclear_reaction.
- Observational_astronomy wikiPageWikiLink Observable_universe.
- Observational_astronomy wikiPageWikiLink Observational_study.
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- Observational_astronomy wikiPageWikiLink Optical_coating.
- Observational_astronomy wikiPageWikiLink Optical_filter.
- Observational_astronomy wikiPageWikiLink Optical_spectrometer.
- Observational_astronomy wikiPageWikiLink Optical_telescope.