Survival times for test particles placed into the ε Cyg stellar binary, in prograde (left) and retrograde coplanar configuration (right). The eccentricity of the orbit of the stellar companion and the initial semi-major axes of the test particles were varied in order to find the stability boundary. The position of the best-fit solution from Sect. 4.3 is plotted by the white diamond; its size is at least by a factor of 10 larger than the uncertainties on the Keplerian parameters.