  VLT-Interferometry will allow imaging of the Galactic Center (GC) and the
nuclei of extragalactic sources at an angular resolution of a few
milliarcseconds. VLTI will be a prime instrument to study the immediate
environment of the massive black hole at the center of the Milky Way. With the
MID infrared Interferometric instrument (MIDI) for example the enigmatic
compact dust embedded MIR-excess sources within the central parsec should be
resolvable. Further the observations of external galactic nuclei will allow
unprecedented measurements of physical parameters (i.e. structure and
luminosity) in these systems. With the exception of a few 'self-referencing'
sources these faint-target observations will benefit from the available
off-axis wavefront-correction system. To fully exploit the use of VLTI within
this context, the following questions have to be addressed among others: How
feasible is blind-pointing on (faint) science targets? Are VLTI observations
still efficiently feasible if these faint science targets exceed the usual
angular distance (<=1arcmin) to a GuideStar [...]? How is the fringe-tracking
procedure affected in densely populated regions such as the GC? What
preparatory steps have to be performed to successfully observe these
non-standard targets with the VLTI? In this contribution, we present aspects
for the preparation of VLTI observations, which will be conducted in the near
future. Considering these example observations of the GC region, several
details of observing modes are discussed, which are necessary to observe such
science targets. The final goal is the definition of observational strategies
[...] touching the limits of VLTI observability.
