As mentioned above the inclinometers are temperature sensitive
(5"/degreeC)
so drifts in the zero-points of the meters can be induced by
temperature effects. Such drifts are often seen, and even if not thermal
in source must be accounted for either in the data reduction or by use
of a data-taking strategy that allows for monitoring of the zero-point.
The meters are also affected by acceleration, and they are certainly
exposed to such in their use at JCMT.
The strategy called by INC_cw5 tries to counter these two effects;
it drives the telescope to the following azimuths in succession :
(10) 20 21 22 . . 29 30 10 20 30 31 32 . . 39 40 20 30 40 41 42 . .
creating in this way local references (20, 30, 40 . .) with which to
check for zero-point drifts or jumps, and it ensures that each 10-deg
segment is taken in the same manner as far as accelerations are
concerned. The large CW and CCW slews in this strategy (30 
10, 10 
20, and 20 
30, for instance) hopefully
nullify each other in
terms of the acceleration effect upon the meters. In any case, the data
must be examined afterwards for systematic differences between reference
measures, residual zero-point drifts etc.
If a large difference occurs between one measurement of a reference and
the next then the data between is essentially irreconcilable with those
before and after, and a shorter (10 degree) sweep, with suitable
references should be made later to patch this gap.
INC_cw5 will work CW (clockwise) or CCW, by suitable input. Load and
run it :
INC> load [jcmtuser.inclinometry.progs]INC_cw5
INC> INC_cw5
Current selected resolution is 1degree, but better resolution, perhaps
by a factor of 10, is required at each bump.
In the past, CW and CCW runs have shown significant differences. While
these effects may have been due to poor data, TWO runs in EACH direction
should be taken for security. The CW-CW and CCW-CCW comparisons will show
consistency (or otherwise) in the data-taking method, and CW-CCW
comparisons will reveal any hysteresis.
This will take about 12 hours with the inclinometers at one location !