Covariances between R.A. and decl. velocity at each proper-motion epoch, for the RV, Hipparcos, FGS, DR2 and DR3 model. The “H” epoch is the net proper motion at the Hipparcos epoch calibrated to the DR3 velocity reference by the HGCA, “G-H” is the long-term proper motion derived from the HGCA, “DR2” is the Gaia DR2 reported proper motion after correcting for frame rotation, and “DR3” is the Gaia DR3 proper motion. Both the DR2 and DR3 values have uncertainties inflated according to the multipliers given in the HGCA, DR2 (T. D. Brandt 2018) and eDR3 versions (T. D. Brandt 2021).