A modern single-channel photometer

Next, consider a more modern photometer that uses pulse-counting. It has a ``neutral'' filter in addition to standard uvby filters. The ``neutral'' filter is in series with the passband filters, and is used to determine the dead-time correction. The positions of these two filter mechanisms are recorded as two adjacent digits in the data, so we can treat them as a single filter code; the second digit is 1 when the ``neutral'' filter is in the beam.

There is also a shutter whose position is encoded separately in the data stream: 0 means open, 1 means shut. This can be treated as a second logical filter mechanism.

The photomultiplier in this modern instrument is in a thermoelectrically cooled chamber, regulated to run at C (273 K). Table I.14 shows what we get.

Again, there is only one detector, so we need not include the NDETUSED column.

Descriptor values: NFILTCAR = 2

NDETS = 2

FILTSTAT = MEASURED

FILTCAT = ' ' (blank string)

CONDITION = AVERAGE

Passband sub-table  

NBAND BAND FILTCODE_1 FILTCODE_2 REDLEAK NDETUSED

--- -- ----- ----- ---- ----

1 U 1 any BLOCKED 1

2 B 2 any BLOCKED 1

3 V 3 any ABSENT 1

4 R any 1 BLOCKED 2

5 I any 2 ABSENT 2

6 DARK1 any 1

7 DARK2 any 2

Detector sub-table

NDET DET SNUMBER MODE COOLING

-- -- ---- -- ----

1 PMT S-13 CI MEASURED

2 PMT GAAS CI DRYICE