Pointing sessions are made every one to two weeks; at present, the
fitted pointing parameters yield an absolute pointing accuracy better
than 
(r.m.s.). We also try to keep the receivers as closely
aligned as possible (to about 
, however, alignment can be lost
occasionally). Checking the pointing, focus, and receiver alignment is the
responsibility of the observers (use a planet for alignment checks).
Note that 230 G2 and 230 G1 have foci differing by 0.4 mm.
Using both receivers, you should carefully monitor the focus and
choose a compromise value. Not doing so may result in broadened beams
(e.g. HPW 
and non-gaussian beams on one receiver [2]).