
\command{FOCUS} measurements are done to optimize the position of the
subreflector (secondary) along the telescope axis by maximizing the
intensity of the radiation focussed into the receiver(s).  It is best
done on a strong point source, e.g., on a planet if or when its
angular diameter is less than the beam width at the frequency to
be observed.  It is strongly recommended to do a \command{POINTING}
on the same source before a \command{FOCUS}.

\command{FOCUS} is normally used with \swb\ or \sww.
(With the bolometer \focus\ is done with \sww).

A calibration is not needed for \focus, anyhow it 
will probably already have been done before the 
\pointing\ before the \focus!

After a focus the data processing software displays the results
and you can enter a correction for the observed focus offset 
with the command

\command{SET FOCUS focusCorrection}

Note that this is the total correction, i.e., the previous correction
plus the additional offset found with the \command{FOCUS} observation.

The optiomal focus correction for different receiver bands may be slightly
different, by a few times 0.1~mm, and the observer can decide to optimize
for one particular band or use a compromise value.

\input{inc/pakoIncSaveFocus.tex}


