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.
PPMXL is a catalog of positions, proper motions, 2MASS- and optical
photometry of 900 million stars and galaxies, aiming to be complete
down to about V=20 full-sky. It is the result
of a re-reduction of USNO-B1 together with 2MASS to the ICRS as
represented by PPMX. This service additionally provides improved proper
motions computed according to Vickers et al, 2016
(:bibcode:`2016AJ....151...99V`).
To the extent possible under law, the publisher has waived all copyright and related or neighboring rights to PPMXL. For details, see the `Creative Commons CC0 1.0 Public Domain dedication <http://creativecommons.org/publicdomain/zero/1.0/>`_. Of course, you should still give proper credit when using this data as required by good scientific practice.
.. image:: /static/img/cc0.png
:alt: [CC0]
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