Global parameters with Sets

Section explained how to set up global values for certain parameters such as the ADC factor and bias strip positions using the CCDSETUP program; by doing this you can set values specific to the data you are using. However, if you have data in Sets life becomes a bit more complicated: each chip will have a different ADC factor, so the value to use will depend on which member of the Set is being processed.

To cope with this, CCDSETUP can be used to configure different values for certain parameters according to Set Index value. The parameters which can vary with Set Index are:

• ADC
• BOUNDS
• DEFERRED
• DIRECTION
• EXTENT
• MASK
• RNOISE
• SATURATION

To set up one or more of these values to be specific to certain Set Index values, run CCDSETUP with the BYSET parameter true, and the INDEX parameter equal to the Set Index to which the parameters apply. When USESET is true, CCDPACK programs which use these global parameters will first look for a value specific to the Set Index of the frame being processed, and if there isn't one they will look for the unspecific global value (if there is no global value at all they will use the current parameter value or ask you to enter it or use a default as usual). So, since many of the parameters will probably be the same for all the members of each Set, the easiest thing is to run CCDSETUP for one of the chips (Set Index values), and then run it again for the other ones just giving the values which are different for them.

Here is an example. Suppose that you have a group of images from a three-chip mosaic camera which all use the same global parameters, except that the readout noise and ADC factor is different according to which chip each image comes from. You can configure the global variables like this:

% ccdsetup

  Type "?" for help on any prompt.
  Type "!" if you do not want to set a parameter.

BYSET - Set up values specific to one Set Index? /NO/ > yes
INDEX - Set Index values these parameters are specific to > 1
RESTORE - Use a setup restoration file /NO/ >
LOGTO - Write log to (Logfile,Terminal,Neither,Both) /'Both'/ >
LOGFILE - logfile name /'CCDPACK.LOG'/ >

    CCDSETUP.............................
    =====================================

  Some values are specific to Set Index 1

ADC - Number of electrons per ADU - Set Index 1 /!/ > 1.83
EXTENT - Useful CCD region (xmin,xmax,ymin,ymax) - Set Index 1 /!/ > 13,1018,1,2
048
RNOISE - Readout noise (ADUs) - Set Index 1 /!/ > 8.5
BOUNDS - Pixel indices of bias strips (in pairs) - Set Index 1 /!/ > 1,12,1019,1
024
DIRECTION - Readout direction (X or Y) - Set Index 1 /!/ > X
DEFERRED - Deferred charge (ADUs) - Set Index 1 /!/ >
MASK - Mask data file - Set Index 1 /!/ >
SATURATE - Look for saturated pixels /NO/ >
PRESERVE - Do you want to preserve your input data types /YES/ >
GENVAR - Do you want to generate variance estimates /YES/ > no
NDFNAMES - Associate position lists with NDF names /YES/ >
USESET - Use CCDPACK Set headers if available /YES/ >

  Listing of the current CCDPACK global parameters (Set Index 1)

  Global ADC factor                             : 1.83
  Global output NDF extent (xmin:xmax,ymin:ymax): (13:1018,1:2048)
  Global readout noise (ADUs)                   : 8.5
  Global bias strip bounds                      : (1:12,1019:1024)
  Global readout direction                      : X
  Not looking for saturated pixels
  Data types will be preserved
  Variances will not be generated
  Position lists will be associated with NDFs
  CCDPACK Set header information will be used where available

SAVE - Save CCD parameters for future restoration /NO/ >

Having set up the values for Set Index 1, you can do the same for the other Set Index values, entering the changed values explicitly and leaving the others to default to the ones you have just entered:

% ccdsetup index=2 adc=2.18 rnoise=6.0 accept
% ccdsetup index=3 adc=1.95 rnoise=9.1 accept

You can then see the global configuration using the CCDSHOW command:

% ccdshow

    CCDSHOW
    =======
  Listing of the current CCDPACK global parameters:
  Set Index-keyed values will be shown where available

  Global ADC factor                             : 1.83
                                       Set Index 1 : 1.83
                                       Set Index 2 : 2.18
                                       Set Index 3 : 1.95
  Global output NDF extent (xmin:xmax,ymin:ymax): (13:1018,1:2048)
  Global readout noise (ADUs)                   : 8.5
                                       Set Index 1 : 8.5
                                       Set Index 2 : 6
                                       Set Index 3 : 9.1
  Global bias strip bounds                      : (1:12,1019:1024)
  Global readout direction                      : X
  Not looking for saturated pixels
  Data types will be preserved
  Variances will not be generated
  Position lists will be associated with NDFs
  CCDPACK Set header information will be used if available

Note that Index-specific values are only shown where they were assigned and are different; in the other cases a common value will be shown, and used, for all Set members.

The Set Index values you should use depend on how you have used MAKESET to add the Set headers; they will nearly always be 1, 2, 3, ... up to the number of members in each Set, but if you are unsure you can use the SHOWSET command to see the values they have.

Note that when using CCDPACK with Sets, you should ensure that the USESET parameter is set to true by CCDSETUP; when it is run with BYSET true, USESET will default to true as well.