focusv -- Determine the optimum electronic focus setting.
focusv intable outtable reject
This task determines the best electronic focus setting of any of the four image dissector tubes (IDT's) of the high speed photometer (HSP). The photomultiplier tube (PMT) does not have an electronic focusing mechanism. All measurements should have the same point source target.
Two schemes are used to determine the optimum focus setting: (1) The "flat-top" scheme assumes that count rates are roughly flat-topped near the best focus setting; points lower than a specified fraction of the highest count rate are rejected, and the middle point of the remaining points is taken as the best focus setting. (2) The "centroid" scheme assumes that count rates are roughly symmetric around the best focus setting, lower count rate points are rejected the same way as in the flat-top scheme, and a centroid determination gives the best focus setting from the remaining points, i.e.,
best focus setting = summation (focus setting * count rate) / summation (count rate)Note that the count rate in this equation will be the observed count rate subtracted by the rejection level count rate in order to highlight count rate differences caused by focusing change.
The maximum number of input data points is 1,000.
- intable [file name]
- Name of the input table; this table contains the following columns:
(count_key) Observed count rate; the column name is passed through the 'count_key' parameter (real). (counterr_key) Standard deviation of the observed count rate; the column name is passed through the 'counterr_key' parameter (real). (focus_key) Electronic focus setting; the column name is passed through the 'focus_key' parameter (real). (temp_key) Temperature; the column name is passed through the 'temp_key' parameter (real). 'EPOCH' Epoch of observation (double). 'TRGTNAME' Target name (char*20). 'APERTOBJ' Object aperture name (char*10).
- outtable [file name]
- Name of the output table created by focusv; this table will contain
the following columns:
'FOCUS_FLAT' Best focus setting determined from "flat_top" scheme rounded off to the nearest integer (real). 'FOCUS_CENT' Best focus setting determined from "centroid" scheme rounded off to the nearest integer (real). 'APER_NAME' Aperture name (char*10). 'TRGTNAME' Target name (char*20). 'FOCUS_LO' Lower limit of focus setting of all observations (real). 'FOCUS_HI' Upper limit of focus setting of all observations (real). 'REJECT_LEVEL' Rejection level, as passed from the 'reject' parameter (real). 'TEMP_MEAN' Average temperature of all observed points (real). 'EPOCH_MEAN' Average epoch of all observed points (double). 'NPOINTS' Total number of observed points (int). 'NREJECTS' Total number of rejected points (int).
- reject = 0.[real, min = 0., max = 1.]
- User-specified fraction of the top count rate, data points below this level are rejected.
- (count_key = "DOBJ") [string, allowed values: DOBJ | AOBJ | DSKY | ASKY]
- Column name of the count rate in the input table.
- (counterr_key = "DOBJ_ERR") [string, allowed values = DOBJ_ERR |
- AOBJ_ERR | DSKY_ERR | ASKY_ERR]
Column name of the count rate's standard deviation in the input table.
- (focus_key = "FOCUSD") [string]
- Column name of the focus setting in input table.
- (temp_key = "DET_TEMP") [string]
- Column name of the temperature in input table.
1. Calibrate the electronic focus setting from the input data table xfocusv$input1 and put results in the output table yfocusv$output1. Data which are lower than 90% of the highest count level are rejected in the process. The data in the input table were obtained from the object detector and are analog data type.
hs> focusv "xfocusv$input1" "yfocusv$output1" 0.9 count_key="AOBJ" counterr_key="AOBJ_ERR"