UCAC5: Star Positions and Proper Motions for Over 107 Million Stars

UCAC5 provides mean positions and proper motions for over 107 million stars, derived from a new astrometric reduction of US Naval Observatory all-sky observations. The catalog combines UCAC5 data with Gaia DR1 to achieve typical proper motion accuracies of 1 to 2 mas/yr for stars between 11th and 15th magnitude. This dataset is hosted by NASA and was last updated in March 2026.

Use Cases

• Modeling stellar motions and galactic dynamics based on precise proper motions.
• Calibrating other astrometric surveys using the high-precision reference star positions.
• Studying star cluster kinematics through improved proper motions for fainter stars.
• Cross-matching and validating celestial object catalogs using the all-sky coverage.

Strengths

• Covers over 107 million stars, providing a large-scale all-sky reference.
• Proper motion accuracies of 1 to 2 mas/yr for stars in the 11 to 15 magnitude range.
• Improves upon TGAS proper motions and extends precision to fainter stars.
• Derived from a new reduction using first principles and the TGAS reference catalog.

Limitations

• Column-level documentation is absent; field semantics must be inferred after download.
• Row count is unknown, which may limit suitability assessment.
• Data may reflect temporal bias inherent to the mean observation epoch near 2001.

Provenance

Source

National Aeronautics and Space Administration (NASA), US Naval Observatory.

Collection Method

New astrometric reductions from first principles using TGAS stars as a reference catalog, combined with Gaia DR1 data.

Time Range

Mean observation epoch near 2001.

Freshness

Last updated 2026-03 13 17:32:15.646551; freshness should be verified.

Geography

All-sky coverage.