Top plot: regions of the x-y plane visible to the observer at different times through scattered X-ray photons, in the case of photons originally emitted by an instantaneous flare of Sgr A^∗ (i.e. all photons emitted at t = 0). Bottom plot: regions of the x-y plane visible to the observer through scattered X-rays at time t = 320 yr, in the case of an instantaneous flare (dashed line) and in the case of flares of duration T (coloured maps). The longer the duration of the flare, the thicker the region of the sky observable simultaneously.