
The combination(!) of \onoff\ and \sww\
provides a very high sensitivity in continuum bolometer observations
of compact sources, and excellent baselines for spectroscopy.  

It has the disadvantage that the (emission-free?) off-source positions 
are very close to the source (limited by the maximum Wobbler throw).
Also, the Wobbler direction is fixed in the horizontal system
relative to the telescope,
and therefore in the source system the off-source positions rotate around the 
source position.

For continumm observations, usually a short time per Wobbler phase, $0.25$~s, is
used with small Wobbler offsets (throws); for spectroscopy, largest
possible Wobbler offsets (throws), up to $\pm 120''$ are preferred, 
but then the time per phase must be longer, $1$ -- $2$~s.

