Astrometric results for the single-exposure plates. Panel a: the differences between the coordinates of the UCAC5 stars in the overlapping images at the epoch of each plate. Panels b–d: the differences between the coordinates of all the stars in the plates and the coordinates of the corresponding stars in the Tycho-2, Gaia TGAS, and UCAC5 catalog, respectively, at the epoch of each plate. In all the panels, the size of an image pixel is shown as a box, Gaussian fits are plotted over the histograms, and the Gaussian standard deviations are given.