Relative orbit of Albireo Ac (with respect to Albireo Aa) according to Scardia et al. (2008), including line of nodes (dash-dotted line), focal-point location (cross) and all available observations (including the few most recent ones that were not used for the orbit solution). The plot is in equatorial (J2000) coordinates; the scale is in arcseconds. Blue dots are interferometric, green crosses are visual, and red H marks HIPPARCOS measurements. The Roberts & Mason (2018) orbit is indicated for comparison (dashed ellipse). The slightly increasing residuals at the end of the observations, that is at the end of the covered orbital arc, motivated the orbit solution of Roberts & Mason (2018).