  We examine the distance of the two galactic microquasars GRO J1655-40 and
A0620-00, which are potentially the two closest black holes to the Sun. We aim
to provide a picture as wide and complete as possible of the problem of
measuring the distance of microquasars in our Galaxy. The purpose of this work
is to fairly and critically review in great detail every distance method used
for these two microquasars in order to show that the distances of probably all
microquasars in our galaxy are much more uncertain than currently admitted.
Moreover, we show that many confirmations of quantitative results are often
entangled and rely on very uncertain measurements. We also present a new
determination of the maximum distance of GRO J1655-40 using red clump giant
stars, and show that it confirms our earlier result of a distance less than 2
kpc instead of 3.2 kpc. Since it then becomes more likely that GRO J1655-40
could originate from the stellar cluster NGC 6242, located at 1.0 kpc, we
review the distance estimations of A0620-00, which is so far the closest black
hole with an average distance of about 1.0 kpc. We show that the distance
methods used for A0620-00 are also problematic. Finally, we present a new
analysis of spectroscopic and astrometric archival data on this microquasar,
and apply the maximum-distance method of Foellmi et al. (2006). It appears that
A0620-00 could indeed be even closer to the Sun than currently estimated, and
consequently would be the closest known black hole to the Sun.
