Tip-tilt effect on the attenuation of the interferometric throughput at the centre of the field of view. The figure also shows the level of attenuation where a quiescent K = 16.5 or bright flaring K = 14.5 Sgr A* reaches the assumed K = 18 detection limit. A quiescent Sgr A* would no longer be observable above ∼37 mas tip-tilt rms, whereas a bright flare would still be observable past 60 mas.