  The Event Horizon Telescope (EHT) has recently published the first images of
the supermassive black hole at the center of our Galaxy, Sagittarius A* (Sgr
A*). Imaging Sgr A* is plagued by two major challenges: variability on short
(approximately minutes) timescales and interstellar scattering along our line
of sight. While the scattering is well studied, the source variability
continues to push the limits of current imaging algorithms. In particular,
movie reconstructions are hindered by the sparse and time-variable coverage of
the array. In this paper, we study the impact of the planned Africa Millimetre
Telescope (AMT, in Namibia) and Canary Islands telescope (CNI) additions to the
time-dependent coverage and imaging fidelity of the EHT array. This African
array addition to the EHT further increases the eastwest (u, v) coverage and
provides a wider time window to perform high-fidelity movie reconstructions of
Sgr A*. We generated synthetic observations of Sgr A*'s accretion flow and used
dynamical imaging techniques to create movie reconstructions of the source. To
test the fidelity of our results, we used one general-relativistic
magneto-hydrodynamic model of the accretion flow and jet to represent the
quiescent state and one semi-analytic model of an orbiting hotspot to represent
the flaring state. We found that the addition of the AMT alone offers a
significant increase in the (u, v) coverage, leading to robust averaged images
during the first hours of the observating track. Moreover, we show that the
combination of two telescopes on the African continent, in Namibia and in the
Canary Islands, produces a very sensitive array to reconstruct the variability
of Sgr A* on horizon scales. We conclude that the African expansion to the EHT
increases the fidelity of high-resolution movie reconstructions of Sgr A* to
study gas dynamics near the event horizon.

Instrumentation and Methods for Astrophysics;High Energy Astrophysical Phenomena