Contours of the angular separation at the time of RS crossing, |$\alpha _{\rm RS}$|⁠, as a function of |$\Gamma _0$| and |$\theta$| for a source with our representative XRB parameters at a distance of |$D=3$| kpc. The angular separation is calculated directly from equation (32) and the red line marks a MeerKAT nominal angular resolution of |$5.4\,\mathrm{ arcsec}$|⁠, with the hashes showing the side of the line where |$\alpha _{\rm RS} < 5.4\,\mathrm{ arcsec}$|⁠. The pink band shows the approximate initial Lorentz factor range for XRBs.