Differences in u_S and θ angles determined from DE431 and EPM2017H ephemerides. Just the differences whose absolute values are larger than 1° are plotted. They are a small fraction of the total (0.45% and 0.02%, respectively), but are not necessarily related to the impulsive events of retrograde motion (see Sect.3.3). The largest differences in u_S (e.g. around 1672.6) are related to low values of solar velocity.