The HSOY Catalog

HSOY is a catalog of 583'001'653 objects with precise astrometry based on PPMXL and Gaia DR1. Typical formal errors at mean epoch in proper motion are below 1 mas/yr for objects brighter than 10 mag, and about 5 mas/yr at the faint end (about 20 mag). South of -30 degrees, astrometry is significantly worse. HSOY also contains, where available, USNO-B, Gaia, and 2MASS photometry. HSOY's positions and proper motions are given for epoch J2000. The catalog becomes severely incomplete faintwards of 16 mag in the G-band. The mean epochs are typically very close to Gaia's J2015.

HSOY still contains about 0.7% spurious close "binaries" (non-matched stars) from the original USNO-B (marked with non-NULL clone). Also, failed matches within Gaia DR1 contribute another 1.5% spurious pairs (marked with non-NULL comp). In both cases, astrometry presumably is sub-standard.

More information is available at

Coordinates (as h m s, d m s or decimal degrees), or SIMBAD-resolvable object
Search radius in arcminutes
Mean magnitude in the G band from Gaia DR1. Magnitudes for which err_flux/flux>0.1 have been dropped.
K_s selected default magnitude from 2MASS
Unique source identifier
The PPMXL object identifier, which in turn is the q3c ipix of the original USNO-B object; for HSOY, only (ipix, comp) is a unique identifier (primary key). The recommended identifier form is 'HSOY ipix.comp', where comp=0 for NULL comps. This is what the SCS generates.
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This means, in particular, that services built on top of large tables may currently be broken. Since our replacement server is much slower than our usual machine, restoring them will take quite some time.

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