Upper panel: spectroscopic versus Strömgren  [α/Fe]  estimates for our 1498 calibrating stars. Crosses (circles) are stars having probability  > 90 percent of being thin (thick) disc based on their kinematic (using U,V,W velocities from the GCS). Downward triangles are stars with lower probability or for which kinematic information was not available. Filled squares are stars having  [Fe/H]  ≤  − 1 (independently of their kinematic thin/thick membership, if available). Lower panel: same symbols as above, showing the difference spectroscopic minus ours.