National Geographic Society - Palomar Observatory Sky Survey
Encyclopedia
The National Geographic Society – Palomar Observatory Sky Survey (NGS-POSS) is a major photographic survey of the night sky
that was completed at Palomar Observatory
in 1958.
at Palomar Observatory
, and the Survey was funded by a grant from the National Geographic Society
to the California Institute of Technology
. Among the primary minds behind the project were Edwin Hubble
, Milton L. Humason
, Walter Baade
, Ira Sprague Bowen
and Rudolph Minkowski
. The first plate was exposed on November 11, 1949. 99% of the plates were taken by June 20, 1956, but the final 1% was not completed until December 10, 1958.
The Survey utilized 14-inch square photographic plates, covering about 6° of sky per side (approximately 36 square degrees per plate). Each region of the sky was photographed twice, once using a red sensitive Kodak 103a-E plate, and once with a blue sensitive Kodak 103a-O plate. This allowed the color of celestial objects to be recorded.
The Survey was originally meant to cover the sky from the north celestial pole to -24° declination. This figure specifies the position of the plate center, hence the actual coverage under the original plan would have been to approximately -27°. It was expected that 879 plate pairs would be required. However the Survey was ultimately extended to -30° plate centers, giving irregular coverage to as far south as -34° declination, and utilizing 936 total plate pairs.
The limiting magnitude
of the survey varied depending on the region of the sky, but is commonly quoted as 22nd magnitude on average.
The California Institute of Technology bookstore used to sell prints of selected POSS regions. The regions were chosen to support educational exercises and the set was a curriculum teaching tool.
In 1962, the Whiteoak Extension, comprising 100 red-sensitive plates extending coverage to -42° declination, was completed and published as identically-sized photographic negative prints. The Whiteoak Extension is often found in libraries stored as an appendix or companion to the photographic print edition of the NGS-POSS. This brings the number of prints to 1,972 for most holders of a photographic edition of the NGS-POSS.
In 1981, a set of NGS-POSS Transparency Overlay Maps was published by Robert S. Dixon of the Ohio State University
. This work is commonly found wherever a photographic print edition of the NGS-POSS is held.
s are partial derivatives of the NGS-POSS, which was used for decades for purposes of cataloging and categorizing celestial objects, especially in studies of galaxy morphology.
Innumerable astronomical object
s were discovered by astronomers studying the NGS-POSS photographs.
In 1986, work was begun on a digital version of the NGS-POSS. Eight years later, the scanning of the original NGS-POSS plates was completed. The resulting digital images were compressed and published as the Digitized Sky Survey
in 1994. The Digitized Sky Survey was made available on a set of 102 CD-ROMs, and can also be queried through several web interfaces.
In 1996, an even more compressed version, RealSky
, was marketed by the Astronomical Society of the Pacific
.
in 2001, a catalog identifying over 89 million objects on the NGS-POSS was placed online as part of the Minnesota Automated Plate Scanner Catalog of the POSS I. The catalog was also distributed in a set of 4 DVD-ROMs. The catalog contains accurate sky positions and brightness measurements for all of these objects as well as more esoteric parameters such as ellipticity, position angle, and concentration index.
Night sky
The term night sky refers to the sky as seen at night. The term is usually associated with astronomy, with reference to views of celestial bodies such as stars, the Moon, and planets that become visible on a clear night after the Sun has set. Natural light sources in a night sky include moonlight,...
that was completed at Palomar Observatory
Palomar Observatory
Palomar Observatory is a privately owned observatory located in San Diego County, California, southeast of Pasadena's Mount Wilson Observatory, in the Palomar Mountain Range. At approximately elevation, it is owned and operated by the California Institute of Technology...
in 1958.
Observations
The photographs were taken with the 48-inch Samuel Oschin telescopeSamuel Oschin telescope
The Samuel Oschin telescope is a 48-inch aperture Schmidt camera at the Palomar Observatory in northern San Diego County, California. It consists of a 49.75-inch Schmidt corrector plate and a 72-inch mirror. The instrument is strictly a camera; there is no provision for an eyepiece to look...
at Palomar Observatory
Palomar Observatory
Palomar Observatory is a privately owned observatory located in San Diego County, California, southeast of Pasadena's Mount Wilson Observatory, in the Palomar Mountain Range. At approximately elevation, it is owned and operated by the California Institute of Technology...
, and the Survey was funded by a grant from the National Geographic Society
National Geographic Society
The National Geographic Society , headquartered in Washington, D.C. in the United States, is one of the largest non-profit scientific and educational institutions in the world. Its interests include geography, archaeology and natural science, the promotion of environmental and historical...
to the California Institute of Technology
California Institute of Technology
The California Institute of Technology is a private research university located in Pasadena, California, United States. Caltech has six academic divisions with strong emphases on science and engineering...
. Among the primary minds behind the project were Edwin Hubble
Edwin Hubble
Edwin Powell Hubble was an American astronomer who profoundly changed the understanding of the universe by confirming the existence of galaxies other than the Milky Way - our own galaxy...
, Milton L. Humason
Milton L. Humason
Milton Lasell Humason was an American astronomer. He was born in Dodge Center, Minnesota.He dropped out of school and had no formal education past the age of 14. Because he loved the mountains, and Mount Wilson in particular, he became a "mule skinner" taking materials and equipment up the...
, Walter Baade
Walter Baade
Wilhelm Heinrich Walter Baade was a German astronomer who worked in the USA from 1931 to 1959.-Biography:He took advantage of wartime blackout conditions during World War II, which reduced light pollution at Mount Wilson Observatory, to resolve stars in the center of the Andromeda galaxy for the...
, Ira Sprague Bowen
Ira Sprague Bowen
Ira Sprague Bowen was an American astronomer. In 1927 he discovered that nebulium was not really a chemical element but instead doubly ionized oxygen.-Life and work:...
and Rudolph Minkowski
Rudolph Minkowski
Rudolph Minkowski was a German-American astronomer. His father was the physiologist Oskar Minkowski and his uncle was Hermann Minkowski....
. The first plate was exposed on November 11, 1949. 99% of the plates were taken by June 20, 1956, but the final 1% was not completed until December 10, 1958.
The Survey utilized 14-inch square photographic plates, covering about 6° of sky per side (approximately 36 square degrees per plate). Each region of the sky was photographed twice, once using a red sensitive Kodak 103a-E plate, and once with a blue sensitive Kodak 103a-O plate. This allowed the color of celestial objects to be recorded.
The Survey was originally meant to cover the sky from the north celestial pole to -24° declination. This figure specifies the position of the plate center, hence the actual coverage under the original plan would have been to approximately -27°. It was expected that 879 plate pairs would be required. However the Survey was ultimately extended to -30° plate centers, giving irregular coverage to as far south as -34° declination, and utilizing 936 total plate pairs.
The limiting magnitude
Limiting magnitude
In astronomy, limiting magnitude is the faintest apparent magnitude of a celestial body that is detectable or detected by a given instrument....
of the survey varied depending on the region of the sky, but is commonly quoted as 22nd magnitude on average.
Publication
The NGS-POSS was published shortly after the Survey was completed as a collection of 1,872 photographic negative prints each measuring 14" x 14". In the early 1970s there was another "printing" of the Survey, this time on 14" x17" photographic negative prints.The California Institute of Technology bookstore used to sell prints of selected POSS regions. The regions were chosen to support educational exercises and the set was a curriculum teaching tool.
In 1962, the Whiteoak Extension, comprising 100 red-sensitive plates extending coverage to -42° declination, was completed and published as identically-sized photographic negative prints. The Whiteoak Extension is often found in libraries stored as an appendix or companion to the photographic print edition of the NGS-POSS. This brings the number of prints to 1,972 for most holders of a photographic edition of the NGS-POSS.
In 1981, a set of NGS-POSS Transparency Overlay Maps was published by Robert S. Dixon of the Ohio State University
Ohio State University
The Ohio State University, commonly referred to as Ohio State, is a public research university located in Columbus, Ohio. It was originally founded in 1870 as a land-grant university and is currently the third largest university campus in the United States...
. This work is commonly found wherever a photographic print edition of the NGS-POSS is held.
Derivative Works
Many astronomical catalogAstronomical catalog
An astronomical catalog or catalogue is a list or tabulation of astronomical objects, typically grouped together because they share a common type, morphology, origin, means of detection, or method of discovery...
s are partial derivatives of the NGS-POSS, which was used for decades for purposes of cataloging and categorizing celestial objects, especially in studies of galaxy morphology.
Innumerable astronomical object
Astronomical object
Astronomical objects or celestial objects are naturally occurring physical entities, associations or structures that current science has demonstrated to exist in the observable universe. The term astronomical object is sometimes used interchangeably with astronomical body...
s were discovered by astronomers studying the NGS-POSS photographs.
In 1986, work was begun on a digital version of the NGS-POSS. Eight years later, the scanning of the original NGS-POSS plates was completed. The resulting digital images were compressed and published as the Digitized Sky Survey
Digitized Sky Survey
The Digitized Sky Survey is a digital version of several photographic atlases of the night sky, and an ongoing project to produce more digital versions of photographic astronomical datasets.- Versions and source material :...
in 1994. The Digitized Sky Survey was made available on a set of 102 CD-ROMs, and can also be queried through several web interfaces.
In 1996, an even more compressed version, RealSky
RealSky
RealSky is the name of a commercially available, digital photographic sky atlas. It is a subset of the Digitized Sky Survey and was published in 1996 by the Astronomical Society of the Pacific....
, was marketed by the Astronomical Society of the Pacific
Astronomical Society of the Pacific
The Astronomical Society of the Pacific is a scientific and educational organization, founded in San Francisco on February 7, 1889. Its name derives from its origins on the Pacific Coast, but today it has members all over the country and the world...
.
in 2001, a catalog identifying over 89 million objects on the NGS-POSS was placed online as part of the Minnesota Automated Plate Scanner Catalog of the POSS I. The catalog was also distributed in a set of 4 DVD-ROMs. The catalog contains accurate sky positions and brightness measurements for all of these objects as well as more esoteric parameters such as ellipticity, position angle, and concentration index.
See also
- Whiteoak extension
- Southern Sky Survey
- Palomar Observatory Sky Survey II
- Two Micron All-Sky Survey2MASSObservations for the Two Micron All-Sky Survey began in 1997 and were completed in 2001 at two telescopes located one each in the northern and southern hemispheres to ensure coverage of the entire sky...
- Sloan Digital Sky SurveySloan Digital Sky SurveyThe Sloan Digital Sky Survey or SDSS is a major multi-filter imaging and spectroscopic redshift survey using a dedicated 2.5-m wide-angle optical telescope at Apache Point Observatory in New Mexico, United States. The project was named after the Alfred P...
- Minnesota Automated Plate Scanner