Differences between USNO-B and PPMXL in positions and proper motions, on an all-sky one-degree grid. At each gridpoint we give the differences X(PPMXL)- X(USNO-B1.0) averaged over all stars in a sqrt(2)/2-degrees environment around the gridpoint given. The corrections given here should bring USNO-B based astrometry to the ICRS.
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