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Astrometric positions of moving objects in the Solar System have beenmeasured using a variety of star catalogs in the past. Previous work has shownthat systematic errors in star catalogs can affect the accuracy of astrometricobservations. That, in turn, can influence the resulting orbit fits for minorplanets. In order to quantify these systematic errors, we compare the positionsand proper motion of stellar sources in the most utilized star catalogs to thesecond release of the Gaia star catalog. The accuracy of Gaia astrometry allowsus to unambiguously identify local biases and derive a scheme that can be usedto correct past astrometric observations of solar system objects. Here weprovide a substantially improved debiasing scheme for 26 astrometric catalogsthat were extensively used in minor planet astrometry. Revised corrections nearthe galactic center eliminate artifacts that could be traced back to referencecatalogs used in previous debiasing schemes. Median differences in stellarpositions between catalogs now tend to be on the order of several tens ofmilliarcseconds (mas) but can be as large as 175 mas. Median stellar propermotion corrections scatter around 0.3 mas/yr and range from 1 to 4 mas/yr forstar catalogs with and without proper motion, respectively. The tables in thiswork are meant to be applied to existing optical observations. They are notintended to correct new astrometric measurments as those should make use of theGaia astrometric catalog. Since previous debiasing schemes already reducedsystematics in past observations to a large extent, corrections beyond thecurrent work may not be needed in the foreseeable future.

Star catalog position and proper motion corrections in asteroid astrometry II: The Gaia era