NGS-POSS and the Evolution of Digital Astronomical Catalogs
The NGS-POSS (National Geographic Society Palomar Observatory Sky Survey) has served as a cornerstone for astronomical research for decades. By providing a comprehensive visual record of the heavens, it has enabled astronomers to catalog and categorize celestial objects with unprecedented precision, particularly in the study of galaxy morphology—the study of the shapes and structures of galaxies.
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The Legacy of Derivative Works
Because of its comprehensive nature, the NGS-POSS has acted as the foundation for numerous derivative astronomical catalogs. A notable example is the Abell Catalog of Planetary Nebulae, which relies on the data provided by the survey. Beyond specific catalogs, the original photographs have led to the discovery of countless astronomical objects, cementing the survey's role in expanding our map of the universe.
The Transition to Digital Formats
As technology advanced, the need to move from physical photographic plates to digital data became apparent. This transition occurred in several key stages:
The Digitized Sky Survey (DSS)
In 1986, efforts began to create a digital version of the NGS-POSS. After eight years of scanning the original plates, the project culminated in 1994 with the release of the Digitized Sky Survey. To manage the massive amount of data, the images were compressed and distributed via a set of 102 CD-ROMs, while also being made accessible through various web interfaces.
RealSky
Following the success of the DSS, the Astronomical Society of the Pacific marketed RealSky in 1996. This version provided an even more compressed format of the survey data, increasing accessibility for researchers and enthusiasts.
The Minnesota Automated Plate Scanner Catalog
The evolution of the survey reached a significant milestone in 2001 with the release of the Minnesota Automated Plate Scanner Catalog of the POSS I. This catalog identified over 89 million objects on the NGS-POSS and was distributed both online and via a set of four DVD-ROMs.
This catalog provides more than just basic identification; it includes precise sky positions and brightness measurements. Furthermore, it offers specialized data known as esoteric parameters, including:
- Ellipticity: The measure of how much an object deviates from being a perfect circle.
- Position Angle: The orientation of the object in the sky.
- Concentration Index: A measure of how the light is distributed within the object.
Key Facts
- The NGS-POSS was fundamental for studying galaxy morphology and creating catalogs like the Abell Catalog of Planetary Nebulae.
- The Digitized Sky Survey (1994) was the result of an eight-year scanning project starting in 1986.
- The Digitized Sky Survey was originally distributed on 102 CD-ROMs.
- RealSky was a highly compressed version of the survey released in 1996.
- The Minnesota Automated Plate Scanner Catalog (2001) identifies over 89 million objects.
| Project/Catalog | Release Year | Primary Format | Key Feature |
|---|---|---|---|
| Digitized Sky Survey | 1994 | 102 CD-ROMs / Web | First digital version of plates |
| RealSky | 1996 | Compressed Digital | High compression for accessibility |
| Minnesota Automated Plate Scanner | 2001 | 4 DVD-ROMs / Web | 89 million objects with detailed parameters |
Frequently Asked Questions
What is the primary use of the NGS-POSS in astronomy?
The NGS-POSS has been used for decades to catalog and categorize celestial objects, with a particular emphasis on the study of galaxy morphology.
How was the Digitized Sky Survey distributed?
The Digitized Sky Survey was published in 1994 and made available through a set of 102 CD-ROMs as well as several web interfaces.
What is RealSky?
RealSky is a highly compressed version of the NGS-POSS data that was marketed by the Astronomical Society of the Pacific in 1996.
How many objects are identified in the Minnesota Automated Plate Scanner Catalog?
The catalog identifies over 89 million objects on the NGS-POSS.
What specific data does the Minnesota Automated Plate Scanner Catalog provide?
It provides accurate sky positions, brightness measurements, and esoteric parameters such as concentration index, position angle, and ellipticity.