skyregion

SkyRegion is a term used in astronomy and data management to describe a defined portion of the celestial sphere. A SkyRegion is specified by boundaries in a coordinate system and is used to organize observations, catalogs, and analyses across large sky surveys.

Common coordinate systems include equatorial (right ascension and declination), galactic (l and b), and ecliptic. SkyRegions can be simple rectangles, circles, or polygonal footprints; many projects employ standardized tiling schemes that subdivide the sphere into uniform regions for efficient querying and processing.

Popular tiling schemes include HEALPix and the Multi-Order Coverage (MOC) map approach. These allow regions to be described compactly and to be queried rapidly by software when retrieving data or cross-matching catalogs.

In practice, SkyRegions are used to plan observations, partition data archives, assign exposure and observing conditions, and enable reproducible analyses by fixing the spatial scope of a study.

Large optical and infrared surveys such as the Sloan Digital Sky Survey, Gaia, and the Vera C. Rubin Observatory's Legacy Survey of Space and Time rely on SkyRegion concepts to organize millions or billions of sources across the sky.

SkyRegion is a flexible concept that also appears in space-based and ground-based projects for time-domain studies, cross-survey comparisons, and archival data management.