Parallax difference before (top) and after correction (bottom) as a function of G magnitude for Kepler (left), K2 (middle), and TESS (right). The grey scatter corresponds to the entire sample of RGB and RC stars. Our best sample with low-extinction RC stars is shown with purple points, and the colour scale indicates their density (increasing from dark purple to white). The red, yellow, and blue lines show the running mean and its uncertainty for each field.