Guide Star Catalog: Photometric Calibrations for 945 Million Stars

945,592,683 stars out to magnitude 21 are cataloged in the GSC-II. This photometric data was compiled to support the Hubble Space Telescope with targeting off-axis stars. The catalog is provided by the National Aeronautics and Space Administration and was last updated in March 2026.

Use Cases

• Calibrating telescope pointing and targeting systems based on off-axis star data.
• Training machine learning models for star detection and classification using photometric magnitudes.
• Conducting statistical analysis of stellar populations and distributions across the sky.
• Supporting astronomical research that requires a large, foundational catalog of stellar positions and brightness.

Strengths

• Catalog contains a specific count of 945,592,683 stars.
• Includes stars down to a defined magnitude limit of 21.
• Data originates from the authoritative source, the National Aeronautics and Space Administration.

Limitations

• Column-level documentation is absent; field semantics must be inferred after download.
• Row count is unknown, which may limit suitability assessment.
• Data is provided in a BIN format, which may require specialized tools to read.

Provenance

Source

National Aeronautics and Space Administration

Collection Method

Compiled to support the Hubble Space Telescope.

Freshness

Last updated 2026-03-13 17:17:40.608007; freshness should be verified.