Next, consider a more elaborate UBVRI photometer with two channels (a ``red'' and a ``blue'' tube). We suppose it has separate filter wheels in the two beams; the first filter wheel contains the UBV filters, and the second has the R and I filters. Filter position 0 in each wheel is opaque; note that we need separate DARK codes for the two channels. Red leaks are blocked, and filter temperatures are measured.
If the filter wheels had been in series instead of
in separate beams, the unused wheel
would have to be set to a clear position, instead of the ``any'' entered in
the first five lines of
Table 
.
Because we have two detectors, the NDETUSED column is mandatory; see
Table .
In our example, the ``blue'' tube is uncooled, but its temperature is measured;
while the ``red'' tube is cooled with dry ice.
Both run in charge-integration mode.
Table: Instrument table file for a simple CCD setup