Photographic plates were one of the earliest forms of photographic film, in which a light-sensitive emulsion of silver salts was applied to a glass plate. This form of photographic emulsion largely faded from the consumer market in the early years of the 20th century, as more convenient and less fragile films were introduced. However, photographic plates were in wide use by the professional astronomical community as late as the 1990s. Such plates respond to ~2% of light received. 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. ... General Name, Symbol, Number silver, Ag, 47 Chemical series transition metals Group, Period, Block 11, 5, d Appearance lustrous white metal Atomic mass 107. ... This article refers to the material. ... Lunar astronomy: the large crater is Daedalus, photographed by the crew of Apollo 11 as they circled the Moon in 1969. ... The 1990s decade refers to the years from 1990 to 1999, inclusive. ... 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. ...

Glass plates were far superior to film for research-quality imaging because they were extremely stable and less likely to bend or distort, especially in large-format frames for wide-field imaging. Many famous astronomical surveys were taken using photographic plates, including the first Palomar Observatory Sky Survey (POSS) of the 1950s, the follow-up POSS-II survey of the 1990s, and the UK Schmidt survey of southern declinations. Many observatories, including Harvard University and Sonneberg Observatory, maintain large archives of photographic plates, primarily for historical research on variable stars. Research is often described as an active, diligent, and systematic process of inquiry aimed at discovering, interpreting and revising facts. ... Palomar Observatory is a privately-owned observatory located in San Diego County, California, 90 miles (145 km) southeast of Mount Wilson Observatory, on Palomar Mountain. ... A Schmidt camera is an astronomical camera designed to provide wide fields of view with limited aberrations. ... Timeline of astronomical maps, catalogs and surveys 1800 BC - Babylonian star catalog 350 BC - Shin Shens star catalog has almost 800 entries 300 BC - star catalog of Timocharis of Alexandria 134 BC - Hipparchus makes a detailed star map ca. ... In astronomy, declination (dec) is one of the two coordinates of the equatorial coordinate system, the other being either right ascension or hour angle. ... Observatory of Strasbourg An observatory is a location used for observing terrestrial and/or celestial events. ... Harvard University is a private university in Cambridge, Massachusetts, USA and a member of the Ivy League. ... Sonneberg Observatory is an astronomical observatory was an institute of the Academy of Science in the German democratic republic. ... Most stars are of nearly constant luminosity. ...

Many solar system objects were discovered by using photographic plates, superseding earlier visual methods. Discovery of minor planets using photographic plates was pioneered by Max Wolf beginning with his discovery of 323 Brucia in 1891. The first natural satellite discovered using photographic plates was Phoebe in 1898. Pluto was discovered using photographic plates in a blink comparator; its moon Charon was discovered by carefully examining a bulge in Pluto's image on a plate. Minor planets, or planetoids are minor bodies of the Solar system orbiting the Sun (or of other planetary systems orbiting other stars) that are larger than meteoroids (the largest of which might be taken to be around 10 meters or so across) but smaller than major planets (Mercury having a... Maximilian Franz Joseph Cornelius Wolf (June 21, 1863 – October 3, 1932) was a German astronomer. ... 323 Brucia was the first asteroid to be discovered by the use of astrophotography. ... 1891 (MDCCCXCI) was a common year starting on Thursday (see link for calendar). ... Moons of solar system scaled to Earths Moon The common noun moon (not capitalized) is used to mean any natural satellite of the other planets. ... For other meanings see Phoebe. ... 1898 (MDCCCXCVIII) was a common year starting on Saturday (see link for calendar) of the Gregorian calendar (or a common year starting on Monday of the 12-day-slower Julian calendar). ... Atmospheric characteristics Atmospheric pressure 0. ... This blink comparator at Lowell Observatory was used in the discovery of Pluto. ... Charon (shair-ən or kair-ən, IPA , Greek Χάρων) is the largest satellite of Pluto. ...

Photographic plates were also an important tool in early high-energy physics, as they get blackened by ionizing radiation. For example, Victor Franz Hess discovered, in the 1910s, cosmic radiation as it left traces on stacks of photographic plates, which he for that purpose brought up on high mountains or let mount into the even higher atmosphere using balloons. Particle physics is a branch of physics that studies the elementary constituents of matter and radiation, and the interactions between them. ... Ionizing radiation is a type of particle radiation in which an individual particle (for example, a photon, electron, or helium nucleus) carries enough energy to ionize an atom or molecule (that is, to completely remove an electron from its orbit). ... Victor Francis Hess (June 24, 1883 – December 17, 1964) was an Austrian-American physicist. ... // Events and trends The 1910s represent the culmination of European militarism which had its beginings during the second half of the 19th Century. ... Cosmic rays can loosely be defined as energetic particles originating outside of the Earth. ... Balloons, like greeting cards or flowers, are given for special occasions. ...

Use of photographic plates has declined significantly since the 1990s, replaced by charge-coupled devices (CCD). CCD cameras have several benefits over glass plates, including highly efficient, linear response to light, and simplicity of image acquisition and processing. However, even the largest format CCDs (e.g. 8192x8192 pixels) still do not have the resolution of most photographic plates, which has forced modern survey cameras to use large arrays of CCD chips. The longevity of electronic data and data formats (such as FITS) is also uncertain. A specially developed CCD used for ultraviolet imaging in a wire bonded package. ... Digital image processing is the use of computer algorithms to perform image processing on digital images. ... Image resolution describes the detail an image holds. ... FITS or Flexible Image Transfer System is the most commonly used file format in astronomy. ...

References

• Peter Kroll, Constanze La Dous, Hans-Jürgen Bräuer: "Treasure Hunting in Astronomical Plate Archives." (Proceedings of the international Workshop held at Sonneberg Observatory, March 4 to 6, 1999.) Verlag Herri Deutsch, Frankfurt am Main (1999), ISBN 3817115997

See also

• film base

Film base is a transparent substrate which acts as a support medium for the photosensitive emulsion that lies atop it. ...

External links

• The Sonneberg Plates Archiv (Sonneberg Observatory)