  We report on the astrometric registration of VLBI images of the SiO and water
masers in OH231.8+4.2, the iconic Proto-Planetary Nebula also known as the
Calabash nebula, using the KVN and Source/Frequency Phase Referencing. This,
for the first time, robustly confirms the alignment of the SiO masers, close to
the AGB star, driving the bi-lobe structure with the water masers in the
out-flow. We are able to trace the bulk motions for the water masers over the
last few decades to be 19 km/s and deduce that the age of this expansion stage
is 38$\pm$2 years. The combination of this result with the distance allows a
full 3D reconstruction, and confirms that the water masers lie on and expand
along the known large-scale symmetry axis and that the outflow is only a few
decades old, so mass loss is almost certainly on-going. Therefore we conclude
that the SiO emission marks the stellar core of the nebular, the water emission
traces the expansion, and that there must be multiple epochs of ejection to
drive the macro-scale structure.
