A modern two-channel photometer

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 I.15.

Because we have two detectors, the NDETUSED column is mandatory; see Table I.15. 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

Descriptor values:

NFILTCAR = 1

NDETS = 1

FILTSTAT = DOME

FILTCAT = ' ' (blank string)

CONDITION = AVERAGE

Passband sub-table

NBAND	BAND	FILTCODE_1	REDLEAK
---	--	-----	----
1	B	B	BLOCKED
2	V	V	BLOCKED

Detector sub-table

NDET	DET	BLUERESP	COOLING	DETTEMP
--	----	----	-----	----
1	SILICON	FRONT	REGULATED	180.