Top frame: central flux nadir of the jet near its base is apparent in the 86 GHz HSA image from Hada et al. (2016; restored with a 0".0001 beam). Bottom frame: surface brightness cross-sections from the image above. The central flux nadir is resolved within 56 M (0".0002) of the EH. The central flux nadir surface brightness is ~ 4%–8% of the average surface brightness on the limbs, 56 M–112 M from the EH and ~ 20–30% of the average surface brightness of the limbs at 140 M.