Mayall telescope at Kitt Peak National Observatory

Observational astronomy is a division of the astronomical science that is concerned with getting data, in contrast with theoretical astrophysics which is mainly concerned with finding out the measureable implications of physical models. It is the practice of observing celestial objects by using telescopes and other astronomical apparatus. Image File history File links Download high resolution version (1200x1600, 494 KB) Photo of the Mayall Telescope (4. ... Image File history File links Download high resolution version (1200x1600, 494 KB) Photo of the Mayall Telescope (4. ... 50 cm refracting telescope at Nice Observatory. ... The Kitt Peak National Observatory (KPNO) is a United States astronomical observatory located on a 2,096 m (6,880 ft) peak of the Quinlan Mountains in the Arizona-Sonoran Desert on the Tohono Oodham Nation, 88 kilometres (55 miles) southwest of Tucson. ... Astronomy (Greek: αστρονομία = άστρον + νόμος, astronomia = astron + nomos, literally, law of the stars) is the science of celestial objects and phenomena that originate outside the Earths atmosphere, such as stars, planets, comets, aurora, galaxies, and the cosmic background radiation. ... The scope of this article is limited to the empirical sciences. ... Theoretical astrophysics is the discipline that seeks to explain the phenomena observed by astronomers in physical terms with a theoretic approach. ... An abstract model (or conceptual model) is a theoretical construct that represents physical, biological or social processes, with a set of variables and a set of logical and quantitative relationships between them. ... 50 cm refracting telescope at Nice Observatory. ...

As a science, 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. The deepest visible-light image of the cosmos, the Hubble Ultra Deep Field. ... Most stars are of nearly constant luminosity. ... NGC 4414, a typical spiral galaxy in the constellation Coma Berenices, is about 56,000 light years in diameter and approximately 60 million light years distant. ...

Unaided eye

Prior to the discovery of the telescope, early observational astronomy relied upon the unaided eye and various instruments for measuring time and direction. Tycho Brahe is noted for his systematic observations of the heavens, and the data he collected was used by Johannes Kepler to build his laws of planetary motion. 50 cm refracting telescope at Nice Observatory. ... Tycho Brahe , born Tyge Ottesen Brahe (December 14, 1546 – October 24, 1601), was a Danish (Scanian) nobleman astronomer as well as an astrologer and alchemist. ... Johannes Kepler Johannes Kepler (December 27, 1571 – November 15, 1630), a key figure in the scientific revolution, was a German mathematician, astrologer, astronomer, and an early writer of science fiction stories. ...

The heavens have been regarded by humans for much of recorded history. Ancient stone structures were built as a means of measuring the passage of time based on the movements of the Sun. Constellations were specific patterns of stars in the sky that came to be associated with particular seasons on the Earth, as well as much lore and mythology. The Sun is the star at the center of Earths solar system. ... Orion is a remarkable constellation, visible from most places on the globe (but not always the whole year long). ... The Pleiades star cluster A star is a massive body of plasma in outer space that is currently producing or has produced energy through nuclear fusion. ... Earth is the third planet in the solar system. ...

The eye can also make other observations of the heavens without the use of a telescope. Ancient records recorded the occurrence of very bright stars (supernovae) that would suddenly appear in the sky, even being viewed during the daylight. There were also records of comets as portents of calamities, and shooting stars that crossed the sky. In modern times, meteorites are collected on the icy plains of Antarctica, and are studied to determine the properties of asteroids and even the surface of Mars. Multiwavelength X-ray image of the remnant of Keplers Supernova, SN 1604. ... An asteroid is a small, solid object in our Solar System, orbiting the Sun. ... For the Roman god, see Mars (mythology). ...

Telescopes

Galileo Galilei was the first person known to have turned a telescope to the heavens and to record what he saw. Since that time, observational astronomy has made steady advances with each improvement in telescope technology. Portrait of Galileo Galilei by Giusto Sustermans. ... 50 cm refracting telescope at Nice Observatory. ...

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 dekametre 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, as well as studies of neutrinos and cosmic rays.

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. Optical astronomy encompasses a wide variety of observations via telescopes that are sensitive in the range of visible light. ... Prism splitting light Light is electromagnetic radiation with a wavelength that is visible to the eye (visible light) or, in a technical or scientific context, electromagnetic radiation of any wavelength. ... Visible light astronomy encompasses a wide variety of observations via telescopes that are sensitive in the range of visible light. ... The wavelength is the distance between repeating units of a wave pattern. ... To help compare different orders of magnitude this page lists lengths between 100 nm and 1 µm (10-7 and 10-6 m). ... Infrared astronomy is the branch of astronomy and astrophysics which deals with objects visible in infrared (IR) radiation. ... Image of a small dog taken in mid-infrared (thermal) light (false color) Infrared (IR) radiation is electromagnetic radiation of a wavelength longer than visible light, but shorter than microwave radiation. ... To help compare different orders of magnitude this page lists lengths between 10-6 and 10-5 m (1 µm and 10 µm). ... Microwave image of 3C353 galaxy at 8. ... Radiation has a variety of different meanings. ... To help compare different orders of magnitude this page lists lengths between 10-3 m and 10-2 m (1 mm and 1 cm). ... To help compare different orders of magnitude this page lists lengths between 10 m and 100 m. ... The 64 metre radio telescope at Parkes Observatory In contrast to an ordinary telescope, which produces visible light images, a radio telescope sees radio waves emitted by radio sources, typically by means of a large parabolic (dish) antenna, or arrays of them. ... High energy astronomy is the study of astronomical objects that release EM radiation of highly energetic wavelengths. ... ROSAT image of X-ray fluorescence of, and occultation of the X-ray background by, the Moon. ... Gamma-ray astronomy is the astronomical study of the cosmos with gamma rays. ... UV astronomy is the branch of astronomy and astrophysics which deals with objects visible in ultraviolet (UV) radiation. ... The neutrino is an elementary particle. ... Cosmic rays can loosely be defined as energetic particles originating outside of the Earth. ... Water vapor or water vapour, also aqueous vapour, is the gas phase of water. ...

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. Far infrared astronomy is the branch of astronomy and astrophysics which deals with objects visible in far-infrared radiation (approximatively from 30μm to 300μm). ... Balloons, like greeting cards or flowers, are given for special occasions. ... An Air shower is an extensive (many kilometres wide) cascade of ionized particles and electromagnetic radiation produced in the atmosphere when a primary cosmic ray (i. ...

Optical telescopes

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. An optical telescope is a telescope which is used to gather, and focus light, for directly viewing a magnified image, making a photograph, etc. ... Legend: γ = Gamma rays HX = Hard X-rays SX = Soft X-Rays EUV = Extreme ultraviolet NUV = Near ultraviolet Visible light NIR = Near infrared MIR = Moderate infrared FIR = Far infrared Radio waves: EHF = Extremely high frequency (Microwaves) SHF = Super high frequency (Microwaves) UHF = Ultrahigh frequency VHF = Very high frequency HF = High frequency... Schematic diagram illustrating how optical wavefronts from a distant star may be perturbed by a turbulent layer in the atmosphere. ... Bulk composition of the moons mantle and crust estimated, weight percent Oxygen 42. ...

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. Layers of Atmosphere - not to scale (NOAA) Outer space, also called just space, refers to the relatively empty regions of the Universe outside the atmospheres of celestial bodies. ... Layers of Atmosphere (NOAA) Earths atmosphere is a layer of gases surrounding the planet Earth and retained by the Earths gravity. ... In physics, an orbit is the path that an object makes, around another object, whilst under the influence of a source of centripetal force, such as gravity. ... Schematic diagram illustrating how optical wavefronts from a distant star may be perturbed by a turbulent layer in the atmosphere. ... The Mauna Kea Observatory, an institute of the University of Hawaii, is considered one of the most important land-based observatories in the world for its isolated, unobstructed views of space without interference from man-made light sources. ... The seeing statistics for Roque de los Muchachos Observatory make it the third best location for optical and infrared astronomy after Dome C, Antarctica and Mauna Kea Observatory, Hawaii. ... Llano de Chajnantor Observatory is an astronomical observatory located at 5104 m altitude in the Chilean Atacama desert, 50 kilometers to the north of San Pedro de Atacama. ... The European Southern Observatory (ESO) is an international astronomical organisation, composed and supported by ten countries from the European Union plus Switzerland and was created in 1962. ... The Cerro Tololo Inter-American Observatory (CTIO) is a complex of astronomical telescopes and instruments located at 30. ... La Silla Observatory is an astronomical observatory in Chile with eighteen telescopes. ...

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. Official language(s) None Capital Largest city Phoenix Phoenix Area  - Total   - Width   - Length    - % water  - Latitude  - Longitude Ranked 6th 113,998 sq mi  295,254 km² 310 miles  500 km 400 miles  645 km 0. ... This photo of New York City shows excessive Sky glow, one form of light pollution, partly caused by many unshielded lights. ...

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. Schematic diagram illustrating how optical wavefronts from a distant star may be perturbed by a turbulent layer in the atmosphere. ... In optics, an aperture is something which restricts the diameter of the light path through one plane in an optical system. ... A deformable mirror can be used to correct wavefront errors in an astronomical telescope. ... Speckle imaging (also known as video astronomy) describes a range of high-resolution astronomical imaging techniques based either on the shift-and-add (image stacking) method or on speckle interferometry methods. ... Aperture synthesis is a type of interferometry that mixes signals from a collection instruments to produce measurements having the same angular resolution as an instrument the size of the entire collection. ... A space observatory is any object in outer space which is used for observation of distant planets, galaxies, and other outer space objects. ...

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). Astrometry is a part of Astronomy and deals with the positions of stars and other celestial bodies, their distances and movements. ... Perturbation is a term used in astronomy to describe alterations to an objects orbit caused by gravitational interactions with other bodies. ... Atmospheric characteristics Atmospheric pressure 120 kPa Hydrogen 83% Helium 15% Methane 1. ... Atmospheric characteristics Surface pressure ≫100 MPa Hydrogen - H2 80% ±3. ... Atmospheric characteristics Atmospheric pressure 0. ... Vulcan was the name given to a small planet proposed to exist in an orbit between Mercury and the Sun, in a 19th century hypothesis which has now been superseded by Albert Einsteins theory of general relativity. ... Atmospheric characteristics Atmospheric pressure trace Potassium 31. ... Precession refers to a change in the direction of the axis of a rotating object. ... Albert Einstein, photographed by Oren J. Turner in 1947. ... It has been suggested that Einsteins theory of gravitation be merged into this article or section. ...

Other instruments

In addition to examination of the universe in the optical spectrum, astronomers have increasingly been able to acquire information in other portions of the electromagnetic spectrum. The earliest such non-optical measurements were made of the thermal properties of the Sun. Instruments employed during a solar eclipse could be used to measure the radiation from the corona. The Sun is the star at the center of Earths solar system. ... The corona is the luminous plasma atmosphere of the Sun extending millions of kilometres into space, most easily seen during a total solar eclipse, but also observable in a coronagraph. ...

Fully-steerable radio telescope in Green Bank, West Virginia.

With the discovery of radio waves, radio astronomy began to emerge as a new discipline in astronomy. The long wavelengths of radio waves required much larger collecting dishes in order to make images with good resolution, and later led to the development of the multi-dish interferometer for making high-resolution aperture synthesis radio images (or "radio maps"). The development of the microwave horn receiver led to the discovery of the microwave background radiation associated with the big bang. Green Bank Telescope: the largest fully steerable single dish in the world, 100 x 110 m. ... Green Bank Telescope: the largest fully steerable single dish in the world, 100 x 110 m. ... Green Bank Telescope: the largest fully steerable single dish in the world, 100 x 110 m. ... Green Bank is located within Pocahontas County, West Virginia (Eastern Region), inside the Allegheny Mountain Range, and can be reached via Hwy 28. ... Microwave image of 3C353 galaxy at 8. ... Interferometry is the applied science of combining two or more input points of a particular data type, such as optical measurements, to form a greater picture based on the combination of the two sources. ... Aperture synthesis is a type of interferometry that mixes signals from a collection instruments to produce measurements having the same angular resolution as an instrument the size of the entire collection. ... In cosmology, the cosmic microwave background radiation (most often abbreviated CMB but occasionally CMBR, CBR or MBR) is a form of electromagnetic radiation discovered in 1965. ... According to the Big Bang theory, the universe emerged from an extremely dense and hot state (bottom). ...

Radio astronomy has continued to expand its capabilities, even using radio astronomy satellites to produce interferometers with baselines much larger than the size of the Earth. However, the ever-expanding use of the radio spectrum for other uses is gradually drowning out the faint radio signals from the stars. For this reason, in the future radio astronomy might be performed from shielded locations, such as the far side of the Moon. The HALCA satellite is an 8 meter diameter radio telescope used for Very Long Baseline Interferometry. ... Far side of the Moon. ... Bulk composition of the moons mantle and crust estimated, weight percent Oxygen 42. ...

The last part of the twentieth century saw rapid technological advances in astronomical instrumentation. Optical telescopes were growing ever larger, and employing adaptive optics to partly negate atmospheric blurring. New telescopes were launched into space, and began observing the universe in the infrared, ultraviolet, x-ray, and gamma ray parts of the electromagnetic spectrum, as well as observing cosmic rays. Interferometer arrays produced the first extremely high-resolution images using aperture synthesis at radio, infrared and optical wavelengths. Orbiting instruments such as the Hubble Space Telescope produced rapid advances in astronomical knowledge, acting as the workhorse for visible-light observations of faint objects. New space instruments under development are expected to directly observe planets around other stars, perhaps even some Earth-like worlds. A deformable mirror can be used to correct wavefront errors in an astronomical telescope. ... Image of a small dog taken in mid-infrared (thermal) light (false color) Infrared (IR) radiation is electromagnetic radiation of a wavelength longer than that of visible light, but shorter than that of microwave radiation. ... Ultraviolet (UV) light is electromagnetic radiation with a wavelength shorter than that of visible light, but longer than soft X-rays. ... In the NATO phonetic alphabet, X-ray represents the letter X. An X-ray picture (radiograph) taken by Röntgen An X-ray is a form of electromagnetic radiation with a wavelength approximately in the range of 5 pm to 10 nanometers (corresponding to frequencies in the range 30 PHz... This article is about electromagnetic radiation. ... Cosmic rays can loosely be defined as energetic particles originating outside of the Earth. ... Aperture synthesis is a type of interferometry that mixes signals from a collection instruments to produce measurements having the same angular resolution as an instrument the size of the entire collection. ... // The Hubble Telescope The Hubble Space Telescope (HST) is a telescope in orbit around the Earth. ...

In addition to telescopes, astronomers have begun using other instruments to make observations. Huge underground tanks have been built to detect neutrino emissions from the Sun and supernovae. Gravity wave detectors are being designed that may capture events such as collisions of massive objects such as neutron stars. Robotic spacecraft are also being increasingly used to make highly detailed observations of planets within the solar system, so that the field of planetary science now has significant cross-over with the disciplines of geology and meteorology. The neutrino is an elementary particle. ... The Sun is the star at the center of Earths solar system. ... Multiwavelength X-ray image of the remnant of Keplers Supernova, SN 1604. ... Gravity is a force of attraction that acts between bodies that have mass. ... Neutron stars are one of the few possible endpoints of stellar evolution. ... A humanoid robot manufactured by Honda. ... A spacecraft is designed to leave Earths atmosphere and operate beyond the surface of the Earth in space. ... A planet is generally considered to be a relatively large mass of accreted matter in orbit around a star that is not a star itself. ... Presentation of the solar system (not to scale) The solar system comprises the Earths Sun and the retinue of celestial objects gravitationally bound to it. ... Planetary science, also known as planetology or planetary astronomy, is the science of planets, or planetary systems, and the solar system. ... Geology (from Greek γη- (ge-, the earth) and λογος (logos, word, reason)) is the science and study of the Earth, its composition, structure, physical properties, history and the processes that shape it. ... Satellite image of Hurricane Hugo with a polar low visible at the top of the image. ...

Observation tools

The key instrument of nearly all modern observational astronomy is the telescope. This serves the dual purposes of gathering more light so that very faint objects can be observed, and magnifying the image so that small and distant objects can be observed. For optical astronomy, the optical components used in a telescope have very exacting requirements which require great precision in their construction. Typical requirements for grinding and polishing a curved mirror, for example, require the surface to be within a fraction of a wavelength of light of a particular conic shape. Many modern "telescopes" actually consist of arrays of telescopes working together to provide higher resolution through aperture synthesis. 50 cm refracting telescope at Nice Observatory. ... In common usage and elementary geometry, a cone (Greek: κώνος) is a solid object obtained by rotating a right triangle around one of its two short sides, the cones axis. ... Aperture synthesis is a type of interferometry that mixes signals from a collection instruments to produce measurements having the same angular resolution as an instrument the size of the entire collection. ...

Large telescopes are housed in domes, both to protect them from the weather and to stabilize the environmental conditions. For example, if the temperature is different from one side of the telescope to the other, the shape of the structure will change, due to thermal expansion, pushing optical elements out of position, and affecting the image. For this reason, the domes are usually bright white (titanium dioxide) or unpainted metal. Domes are often opened around sunset (pointed east, of course!), long before observing can begin, so that air can circulate and bring the entire telescope to the same temperature as the surroundings. In order to prevent wind-buffet or other vibrations affecting observations, it is standard practice to mount the telescope on an independent concrete pier inside the dome/building foundations. In physics, thermal expansion is the tendency of matter to increase in volume or pressure when heated. ... Titanium dioxide, also known as titanium(IV) oxide or titania, is the naturally occurring oxide of titanium, chemical formula TiO2. ...

In order to do almost any scientific work, telescopes must keep track of objects as they wheel across the visible sky. In other words, they must smoothly compensate for the rotation of the Earth. Until the advent of computer controlled drive mechanisms, the standard solution was some form of equatorial mount, and for small telescopes this is still the norm. However, this is a structurally poor design and becomes more and more cumbersome, and as the diameter and weight of the telescope increases. The world's largest equatorial mounted telescope is the 200 inch (5.1 m) Hale Telescope, whereas recent 8-10 m telescopes use the structurally better altasimuth mount, and are actually physically smaller than the Hale, despite the larger mirrors. As of 2006, there are design projects underway for gigantic alt-az telescopes: the Thirty Metre Telescope [1], and the 100 m diameter Overwhelmingly Large Telescope[2] An illustration of a modern personal computer. ... An Equatorial Mount for a telescope. ... The Hale Telescope is the largest telescope at the Palomar Observatory. ... The Overwhelmingly Large Telescope (OWL) is a conceptual design by the European Southern Observatory organization for a telescope which is intended to have a single aperture of 100 meters in diameter. ...

Amateur astronomers use such instruments as the Newtonian reflector, the Refractor and the increasingly popular Maksutov telescope. Newtonian Telescope The Newtonian telescope is a type of reflecting telescope invented by the British scientist Sir Isaac Newton (1643-1727), using a parabolic primary mirror and a flat diagonal secondary mirror. ... A refracting telescope: 1 - tube; 2 - eyepiece; 3 - mountingl; 4 - tripod; 5 - counterweights A refracting or refractor telescope is a type of optical telescope that refracts or bends light at each end using lenses. ... Invented by the Russian optician Dmitri Maksutov (1896-1964), the Maksutov reflecting telescope is a type of catadioptric telescope that uses a spherical primary mirror in conjunction with a meniscus-shaped corrector plate at the entrance pupil in order to correct spherical aberration. ...

The photograph has served a critical role in observational astronomy for over a century, but in the last 30 years it has been largely replaced for imaging applications by digital sensors such as CCDs and CMOS chips. Specialist areas of astronomy such as photometry and interferometry have utilised electronic detectors for a much longer period of time. Astrophotography uses specialised photographic film (or usually a glass plate coated with photographic emulsion), but there are a number of drawbacks, particularly a low quantum efficiency, of the order of 3%, whereas CCDs can be tuned for a QE >90% in a narrow band. Almost all modern telescope instruments are electronic arrays, and older telescopes have been either been retrofitted with these instruments or closed down. Glass plates are still used in some applications, such as surveying, because the resolution possible with a chemical film is much higher than any electronic detector yet constructed. A sepia-tinted photograph of an English couple, taken in 1895. ... A specially developed CCD used for ultraviolet imaging in a wire bonded package. ... Static CMOS Inverter CMOS (see-moss), which stands for complementary metal-oxide-semiconductor, is a major class of integrated circuits. ... Astrophotography is a specialised type of photography that entails making photographs of astronomical objects in the night sky such as planets, stars, and deep sky objects such as star clusters and galaxies. ... Undeveloped Arista black and white film, ISO 125. ... A. Two immisicble liquids, not emulsified; B. An emulsion of Phase B dispersed in Phase A; C. The unstable emulsion progressively separates; D. The (purple) surfactant positions itself on the interfaces between Phase A and Phase B, stabilizing the emulsion An emulsion is a mixture of two immiscible (unblendable) substances. ... A graph showing variation of quantum efficiency with wavelength of the CCD chips in the Hubble Space Telescopes Wide Field and Planetary Camera 2. ...

All astronomy, prior to the invention of photography, was done with the naked eye. However, even before films became really sensitive enough, scientific astronomy moved entirely to film, because of the overwhelming advantages: - The human eye discards what it sees from split-second to split-second, but a photographic film gathers more and more light as long for as long as the shutter is open. - The resulting image is permanent, so many astronomers can use (and argue over!) the same data. - It is possible to see objects as they change over time (SN 1987A is a spectacular example). SN 1987A was a supernova in the outskirts of the Tarantula Nebula in the Large Magellanic Cloud, a nearby dwarf galaxy. ...

The blink comparator is an instrument that is used to compare two nearly identical photographs made of the same section of sky at different points in time. The comparator alternates illumination of the two plates, and any changes are revealed by blinking points or streaks. This instrument has been used to find asteroids, comets, and variable stars. This blink comparator at Lowell Observatory was used in the discovery of Pluto. ... An asteroid is a small, solid object in our Solar System, orbiting the Sun. ... Comet Hale-Bopp For other uses, see Comet (disambiguation). ... Most stars are of almost constant luminosity. ...

The position or cross-wire micrometer is an implement that has been used to measure double stars. This consists of a pair of fine, movable lines that can be moved together or apart. The telescope lens is lined up on the pair and oriented using position wires that lie at right angles to the star separation. The movable wires are then adjusted to match the two star positions. The separation of the stars is then read off the instrument, and their true separation determined based on the magnification of the instrument. External, internal, and depth micrometers A micrometer is a widely used device in mechanical engineering for precisely measuring thickness of blocks, outer and inner diameters of shafts and depths of slots. ... Double Star is a science fiction novel by Robert A. Heinlein. ...

A vital instrument of observational astronomy is the spectrograph. The absorption of specific wavelengths of light by elements allows specific properties of distant bodies to be observed. This capability has resulted in the discovery of the element of helium in the Sun's emission spectrum, and has allowed astronomers to determine a great deal of information concerning distant stars, galaxies, and other celestial bodies. Doppler shift (particularly "redshift") of spectra can also be used to determine the radial motion or distance with respect to the Earth. A spectroscope is a device which measures the spectrum of light. ... General Name, Symbol, Number helium, He, 2 Chemical series noble gases Group, Period, Block 18, 1, s Appearance colorless Atomic mass 4. ... A materials emission spectrum is the amount of electromagnetic radiation of each frequency it emits when it is heated (or more generally when it is excited). ... The Doppler effect is the apparent change in frequency or wavelength of a wave that is perceived by an observer moving relative to the source of the waves. ... Redshift of spectral lines in the optical spectrum of a supercluster of distant galaxies (right), as compared to that of the Sun (left). ... Earth is the third planet in the solar system. ...

Early spectrographs employed banks of prisms that would split the light into a broad spectrum. Later the grating spectrograph was developed, which reduced the amount of light loss compared to prisms and provided higher spectral resolution. The spectrum can be photographed in a long exposure, allowing the spectrum of faint objects (such as distant galaxies) to be measured. If a shaft of light entering a prism is sufficiently small such that the coloured edges meet, a spectrum results In optics, a prism is a device used to refract light, reflect it or break it up (to disperse it) into its constituent spectral colours (colours of the rainbow). ... To meet Wikipedias quality standards, this article or section may require cleanup. ...

Stellar photometry came into use in 1861 as a means of measuring stellar colors. This technique measured the magnitude of a star at specific frequency ranges, allowing a determination of the overall color, and therefore temperature of a star. By 1951 an internationally standardized system of UBV-magnitudes (Ultraviolet-Blue-Visual) was adopted. 1861 is a common year starting on Tuesday. ... Shanil Davendra Singh rules 4 life! ... Temperature is also the name of a song by Sean Paul. ... 1951 (MCMLI) was a common year starting on Monday; see its calendar. ... // Headline text HEY!! HOW ARE YOU ALL?? Its nice of you to come read this page. ...

Photoelectric photometry using the CCD is now frequently used to make observations through a telescope. These sensitive instruments can record the image nearly down to the level of individual photons, and can be designed to view in parts of the spectrum that are invisible to the eye. The ability to record the arrival of small numbers of photons over a period of time can allow a degree of computer correction for atmospheric effects, sharpening up the image. Multiple digital images can also be combined to further enhance the image. When combined with the adaptive optics technology, image quality can approach the theoretical resolution capability of the telescope. The photoelectric effect is the emission of electrons from matter upon the absorption of electromagnetic radiation, such as ultraviolet radiation or x-rays. ... Photometry is a technique of astronomy concerned with measuring the flux, or intensity of an astronomical objects electromagnetic radiation. ... A specially developed CCD used for ultraviolet imaging in a wire bonded package. ... In physics, the photon (from Greek φως, phōs, meaning light) is the quantum of the electromagnetic field; for instance, light. ... A deformable mirror can be used to correct wavefront errors in an astronomical telescope. ...

Filters are used to view an object at particular frequencies or frequency ranges. Multilayer film filters can provide very precise control of the frequencies transmitted and blocked, so that, for example, objects can be viewed at a particular frequency emitted only by excited hydrogen atoms. Filters can also be used to partially compensate for the effects of light pollution by blocking out unwanted light. Polarization filters can also be used to determine if a source is emitting polarized light, and the orientation of the polarization. Coloured and Neutral Density filters An optical filter is a device which selectively transmits light having certain properties (often, a particular range of wavelengths, that is, range of colours of light, or polarizations), while blocking the remainder. ... An optical coating is a thin layer of material placed on an optical component such as a lens or mirror which alters the way in which the optic reflects and transmits light. ... General Name, Symbol, Number hydrogen, H, 1 Chemical series nonmetals Group, Period, Block 1, 1, s Appearance colorless Atomic mass 1. ... This photo of New York City shows excessive Sky glow, one form of light pollution, partly caused by many unshielded lights. ... Polarization is an important phenomenon in astronomy. ...

Observing

Astronomers observe a wide range of astronomical sources, including high-redshift galaxies, AGNs, the afterglow from the Big Bang and many different types of stars and protostars. An active galaxy is a galaxy where a significant fraction of the energy output is not emitted by the normal components of a galaxy: stars, dust and interstellar gas. ... In cosmology, the cosmic microwave background radiation (most often abbreviated CMB but occasionally CMBR, CBR or MBR) is a form of electromagnetic radiation discovered in 1965. ...

A variety of data can be observed for each object. The position coordinates locate the object on the sky using the techniques of spherical astronomy, and the magnitude determines its brightness as seen from the Earth. The relative brightness in different parts of the spectrum yields information about the temperature and physics of the object. Photographs of the spectra allow the chemistry of the object to be examined. See Cartesian coordinate system or Coordinates (elementary mathematics) for a more elementary introduction to this topic. ... Spherical astronomy is the branch of astronomy that is used to determine the location of objects on the celestial sphere, as seen at a particular date, time, and location on the Earth. ... In science, a magnitude is the numerical size of something: see orders of magnitude. ... Earth is the third planet in the solar system. ... Temperature is also the name of a song by Sean Paul. ...

Parallax shifts of a star against the background can be used to determine the distance, out to a limit imposed by the resolution of the instrument. The radial velocity of the star and changes in its position over time (proper motion) can be used to measure its velocity relative to the Sun. Variations in the brightness of the star give evidence of instabilities in the star's atmosphere, or else the presence of an occulting companion. The orbits of binary stars can be used to measure the relative masses of each companion, or the total mass of the system. Spectroscopic binaries can be found by observing doppler shifts in the spectrum of the star and its close companion. Parallax (Greek: παραλλαγή (parallagé) = alteration) is the change of angular position of two stationary points relative to each other as seen by an observer, due to the motion of an observer. ... Radial velocity is the velocity of an object in the direction of the line of sight. ... The proper motion of a star is the motion of the position of the star in the sky (the change in direction in which we see it, as opposed to the radial velocity) after eliminating the improper motions of the stars, which affect their measured coordinates but are not real... The Doppler effect is the apparent change in frequency or wavelength of a wave that is perceived by an observer moving relative to the source of the waves. ...

Stars of identical masses that are formed at the same time and under the similar conditions will typically have nearly identical observed properties. Observing a mass of closely associated stars, such as in a globular cluster, allows data to be assembled about the distribution of stellar types. These tables can then be used to infer the age of the association. A globular cluster is a spherical bundle of stars (star cluster) that orbits a galaxy as a satellite. ...

For distant galaxies and AGNs observations are made of the overall shape and properties of the galaxy, as well as the groupings in which they are found. Observations of certain types of variable stars and supernovae of known luminosity, called standard candles, in other galaxies allows the inference of the distance to the host galaxy. The expansion of space causes the spectra of these galaxies to be shifted, depending on the distance, and modified by the doppler effect of the galaxy's radial velocity. Both the size of the galaxy and its redshift can be used to infer something about the distance of the galaxy. Observations of large numbers of galaxies are referred to as redshift surveys, and are used to model the evolution of galaxy forms. NGC 4414, a typical spiral galaxy in the constellation Coma Berenices, is about 56,000 light years in diameter and approximately 60 million light years distant. ... An active galaxy is a galaxy where a significant fraction of the energy output is not emitted by the normal components of a galaxy: stars, dust and interstellar gas. ... Galaxy groups and clusters are super-structures in the spread of galaxies of the cosmos. ... A Cepheid variable or Cepheid is a member of a particular class of variable stars, notable for a fairly tight correlation between their period of variability and absolute luminosity. ... Multiwavelength X-ray image of the remnant of Keplers Supernova, SN 1604. ... Luminosity has different meanings in several different fields of science. ... A standard candle is an astronomical object that has a known luminosity. ... The Doppler effect, named after Christian Andreas Doppler, is the apparent change in frequency or wavelength of a wave that is perceived by an observer moving relative to the source of the waves. ... Redshift of spectral lines in the optical spectrum of a supercluster of distant galaxies (right), as compared to that of the Sun (left). ... In astronomy, a redshift survey is a survey of a section of the sky to measure the redshift of astronomical objects. ...

See also

• Optical telescopes
• Space observatory
• Timeline of telescopes, observatories, and observing technology

An optical telescope is a telescope which is used to gather, and focus, light, for directly viewing a magnified image, making a photograph, etc. ... A space observatory is any instrument in outer space which is used for observation of distant planets, galaxies, and other outer space objects. ... Timeline of telescopes, observatories, and observing technology. ...

Related lists

• List of observatories
• List of radio telescopes