  We present a statistical analysis of 43 coronal dimming events, associated
with Earth-directed CMEs that occurred during the period of quasi-quadrature of
the SDO and STEREO satellites. We studied coronal dimmings that were observed
above the limb by STEREO/EUVI and compared their properties with the mass and
speed of the associated CMEs. The unique position of satellites allowed us to
compare our findings with the results from Dissauer et al. (2018b, 2019), who
studied the same events observed against the solar disk by SDO/AIA. Such
statistics is done for the first time and confirms the relation of coronal
dimmings and CME parameters for the off-limb viewpoint. The observations of
dimming regions from different lines-of-sight reveal a similar decrease in the
total EUV intensity ($c=0.60\pm0.14$). We find that the (projected) dimming
areas are typically larger for off-limb observations (mean value of
$1.24\pm1.23\times10^{11}$ km$^2$ against $3.51\pm0.71\times10^{10}$ km$^2$ for
on-disk), with a correlation of $c=0.63\pm0.10$. This systematic difference can
be explained by the (weaker) contributions to the dimming regions higher up in
the corona, that cannot be detected in the on-disk observations. The off-limb
dimming areas and brightnesses show very strong correlations with the CME mass
($c=0.82\pm0.06$ and $c=0.75\pm0.08$), whereas the dimming area and brightness
change rate correlate with the CME speed ($c\sim0.6$). Our findings suggest
that coronal dimmings have the potential to provide early estimates of mass and
speed of Earth-directed CMEs, relevant for space weather forecasts, for
satellite locations both at L1 and L5.
