Mean orbital parameters values in the [Mg/Fe] − [Fe/H] plane for the entire MW disc. From left to right: guiding radius (R_guid), pericentre (R_min), apocentre (R_max), eccentricity and maximum vertical excursion (Z_max). The grey lines show the isodensity contours. The white lines correspond to the boundary used to define high- and low-α populations. The top row shows the result of the orbit superposition solution, while the bottom one shows the raw APOGEE data.