-
ADC = _DOUBLE (Read)
-
The Analogue-to-Digital Conversion factor. This number converts
input ADUs to detected electrons. This value is used to
estimate the Poissonian noise in the output (debiassed) data
values. If the EXPAND parameter is true, then the output is
multiplied by ADC so that the output is in counts (electrons)
rather than ADUs. If variances are not being generated
then this value will not be used.
If a global value for this parameter has been set using
CCDSETUP then this will be used. If USESET is true then a
value specific to the Set Index of each image will be sought.
[1.0]
-
BADBITS = _INTEGER (Read)
-
If the first input image has no quality component, and you have
specified the SETBAD= FALSE option, you will be requested to
supply a value for BADBITS (SUN/33). The default for this
is 1. BADBITS is a byte value and hence can only be in the
range 0-255.
[1]
-
BIAS = LITERAL (Read)
-
Name of the image which contains the bias calibration data. This
parameter may be specified as ! in which case either a
constant or values derived from the bias strip(s) are used.
The name of this file may be specified using indirection
through an ASCII file. The offered default is either the last
used master bias name or (if one exists) the name of the image
produced by the last run of MAKEBIAS.
If USESET is true and you are using bias calibration data
from a file, BIAS should be a group expression referring
to one master bias frame matching each of the Set Index
attributes represented in the IN list; again the name of
the file produced by MAKEBIAS will normally be suitable.
[Global master bias or !]
-
BOUNDS( 2 or 4 ) = _INTEGER (Read)
-
The pixel indices (see notes) of the upper and lower bounds of
the bias strip(s). These bounds can run in either the
horizontal or vertical directions. The direction is controlled
by the DIRECTION parameter. The bounds must be supplied in
pairs. Pixel indices are the actual number of pixels, starting
at 1,1 at the lower left hand corner of the image data array,
which includes any origin offsets within the input images.
If global values for these bounds have been set using
CCDSETUP then those values will be used. If USESET is true
then a value specific to the Set Index of each image will
be sought.
-
BOXSIZE( 2 ) = _INTEGER (Read)
-
The sizes of the sides of the box to be used when smoothing the
bias strips. Only used when CMODE="BOX".
[15,15]
-
CMODE = LITERAL (Read)
-
The "clean-up" mode for the bias strips. This parameter may
take values of "BOX", "SIGMA" or "WEIGHT".
If CMODE="BOX" then
the bias strips are smoothed with a box filter before being
processed. If CMODE="SIGMA" then the bias strips are sigma
clipped before being processed. If CMODE="WEIGHT" then only
the weighting as indicated by the WMODE parameter is used to
attempt to decrease the effects of erroneous pixel values.
[BOX]
-
DEFERRED = _DOUBLE (Read)
-
The deferred charge value. This is also often known as the
"fat" or "skinny" zero. It represents the amount of charge
left behind in a pixel on a readout transfer. This value is
subtracted from the data.
If a global value for this parameter has been set using
CCDSETUP then this will be used. If USESET is true then a
value specific to the Set Index of each image will be sought.
[0.0]
-
DIRECTION = LITERAL (Read)
-
The readout direction of the CCD. This parameter can take
values of "X" or "Y". X indicates that the readout direction is
horizontal , Y indicates that the readout direction is
vertical. The BOUNDS parameter values are assumed to be values
along the readout direction.
If a global value for this parameter has been set using
CCDSETUP then this will be used. If USESET is true then a
value specific to the Set Index of each image will be sought.
[X]
-
EXPAND = _LOGICAL (Read)
-
This value controls whether or not the output data should be
multiplied by the ADC factor to convert the input ADUs to
counts (electrons). The output variance is affected accordingly
(multiplied by ADC2). This option is disabled if no variances
are generated. Care should be taken when using this option
with a large ADC factor and data types of _WORD,_UWORD,_BYTE
or _UBYTE as the output data range may exceed that allowed
with these types. In this case the best option is to set
the PRESERVE parameter FALSE.
[Default is TRUE if input data is not an unsigned data type
otherwise FALSE.]
-
EXTENT(4) = _INTEGER (Read)
-
The extent of the useful CCD area. This should be given in
pixel index values (see notes). The extent is restricted to
that of the CCD frame, so no padding of the data can occur. If
values outside of those permissable are given then they are
modified to lie within the CCD frame. The values should be
given in the order XMIN,XMAX,YMIN,YMAX.
Normally the extent should be set so that the bias strips
are excluded from the output data, this is essential for
flatfields whose normalisation could be adversely biased.
If global values for these bounds have been set using
CCDSETUP then those values will be used. If USESET is true then a
value specific to the Set Index of each image will be sought.
-
FMODE = LITERAL (Read)
-
The fit mode which will be used when interpolating bias values.
May take values of "LINE" or "PLANE". This is used together
with the SMODE parameter to define the interpolation method,
ie. FMODE="LINE" & SMODE="LINEAR", fits each row or column of
the bias strips by a straight line; FMODE="PLANE" &
SMODE="CONSTANT" derives a single constant for the bias value;
FMODE="PLANE" & SMODE="LINEAR" fits a plane to the bias-strip
data.
[LINE]
-
GENVAR = _LOGICAL (Read)
-
If variances are to be generated then this value is set
TRUE. If variances are not to be generated then this value
should be set FALSE. Normally variances should be generated,
even though disk and process time savings can be made by their
omission.
If a global value has been set up using CCDSETUP this value
will be used.
[FALSE]
-
GETBIAS = _LOGICAL (Read)
-
This parameter controls whether or not an attempt is to be made
to access a master bias image.
[TRUE]
-
GETMASK = _LOGICAL (Read)
-
This parameter controls whether or not an attempt is to be made
to access a defect mask using the parameter MASK.
[TRUE]
-
IN = LITERAL (Read)
-
A list of the names of the images which contain the raw CCD
data. Note that at present the input data must have a common
processing mode, i.e. have the same ADC factor, readout noise
etc. These values are represented by the parameter values of
the task. The input data must also use the same master bias
frame except if USESET is true and the input and bias images
contain suitable CCDPACK Set header information, in which
case each input image will be processed using the bias image
with the corresponding Set Index attribute.
The image names should be separated by commas and may include
wildcards.
-
KEEPIN = _LOGICAL (Read)
-
Whether to keep (i.e. not delete) the input images (parameter IN)
or not. Deleting the input images has the advantage of saving
disk space, but should probably only be used if this program
is part of a sequence of commands and the intermediary data
produced by it are not important.
The calibration master frames (parameters BIAS and possibly MASK)
are never deleted.
The default for this parameter is TRUE and this cannot be
overridden except by assignment on the command line or in
response to a forced prompt.
[TRUE]
-
LOGFILE = FILENAME (Read)
-
Name of the CCDPACK logfile. If a null (!) value is given for
this parameter then no logfile will be written, regardless of
the value of the LOGTO parameter.
If the logging system has been initialised using CCDSETUP,
then the value specified there will be used. Otherwise, the
default is "CCDPACK.LOG".
[CCDPACK.LOG]
-
LOGTO = LITERAL (Read)
-
Every CCDPACK application has the ability to log its output
for future reference as well as for display on the terminal.
This parameter controls this process, and may be set to any
unique abbreviation of the following:
- TERMINAL - Send output to the terminal only
- LOGFILE - Send output to the logfile only (see the
LOGFILE parameter)
- BOTH - Send output to both the terminal and the
logfile
- NEITHER - Produce no output at all
If the logging system has been initialised using CCDSETUP
then the value specified there will be used. Otherwise, the
default is "BOTH".
[BOTH]
-
MASK = LITERAL (Read)
-
The name of an image or ASCII Regions Definition (ARD) file.
If an image is given then any regions of BAD values (set through
explicit BAD values or by BADBITS in the quality component)
will be transferred to the output image.
If an ARD file is given then its regions will be interpreted
and transferred to the output image. ARD is described in its own
section.
The regions whose quality is to be set are probably hot spots,
line defects etc. which contain little or no useful
information. This parameters may be returned as ! indicating
that no mask is to be applied.
If a global value for this parameter has been set using
CCDSETUP then this will be used. If USESET is true then a
value specific to the Set Index of each image will be sought.
The name of this file may be specified using indirection
through a file.
[!]
-
NSIGMA = _REAL (Read)
-
The number of standard deviations to clip the bias strips at.
This is only used in CMODE="SIGMA". The actual clipping
occurs at NSIGMA*RNOISE. If no variances are being generated
then the RNOISE value is estimated from the data values in
the strips.
[4.0]
-
OFFSET = _LOGICAL (Read)
-
If TRUE then the input bias data array is offset
by the mean value derived from the bias-strip areas. If FALSE
then the bias data is directly subtracted. This parameter is
disabled for unsigned data types as the bias data cannot have
been previously zeroed.
[TRUE]
-
OUT = LITERAL (Write)
-
Names of the output images. These may be specified as list of
comma separated names, using indirection if required, OR,
as a single modification element (of the input names). The
simplest modification element is the asterisk "*" which means
call each of the output images the same name as the
corresponding input images. So:
IN > *
OUT > *
signifies that all the images in the current directory should be
used and the output images should have the same names.
Other types of modification can also occur, such as:
OUT > tmp_*
which means call the output images the same as the input images but
put tmp_ in front of the names. Replacement of a specified
string with another in the output file names can also be used:
OUT > tmp_*|debias|flattened|
this replaces the string debias with flattened in any of the
output names tmp_*.
-
PRESERVE = _LOGICAL (Read)
-
If TRUE then the data type of the input images are used for
processing and are preserved on exit from this routine. If
FALSE then a suitable floating point type will be chosen for
the output type and the processing will be performed using
this choice.
This option should be used when a unacceptable loss of
accuracy may occur, or when the data range can no longer be
represented in the range of the present data type. The latter
effect may occur when expanding input ADU values into
electrons, if the ADC factor is large and the input data have
types of _WORD,_UWORD,_BYTE or _UBYTE.
If a global value for this parameter has been set using
CCDSETUP then this will be used.
[TRUE]
-
RNOISE = _DOUBLE (Read)
-
The readout noise in input data units (ADUs). An estimate of
the readout noise is shown for unweighted values in the bias
strips, if the bias strips are used. If variances are not
generated then this value is not used. If variances are
generated then the readout noise is included in the variance
estimates.
If a global value has been set using CCDSETUP then this will
be used. If USESET is true then a value specific to the
Set Index of each image will be sought.
[Dynamic default or 1.0]
-
SATURATE = _LOGICAL (Read)
-
This parameter controls whether the data are to be processed to
detect saturated values or not. The actual saturation value is
given using the SATURATION parameter.
[FALSE]
-
SATURATION = _DOUBLE (Read)
-
The data saturation value. Only used if SATURATE is TRUE.
If a global value has been set using CCDSETUP then this will
be used. If USESET is true then a value specific to the
Set Index of each image will be sought.
[1.0D6]
-
SETBAD = _LOGICAL (Read)
-
If TRUE then the quality information will be transferred
from the MASK image to the output images in the form of BAD
("flagged") values in the data component. This is the usual
method of indicating the presence of pixels with no value. If
FALSE then the quality information will be transferred into
the quality component, all output quality pixels will have
their BADBITS set. (Note that if the input image already has a
quality component the BADBITS will be set by a logical OR of
the current bits with the BADBITS value).
[TRUE]
-
SETSAT = _LOGICAL (Read)
-
This parameter controls how saturated data will be flagged.
If it is set TRUE then saturated values will be replaced by
the value of the parameter SATURATION (which is also the value
used to detect saturated data). If it is FALSE then saturated
values will be set to BAD (also known as invalid).
[FALSE]
-
SMODE = LITERAL (Read)
-
The mode which will be used to perform any interpolation fit
between the bias strips. Can take values of "CONSTANT" or
"LINEAR". If only one bias strip is given this may only take
the value "CONSTANT". This is used together with the FMODE
parameter to define the interpolation method, i.e.
FMODE="LINE", SMODE="LINEAR", fits each row or column of the
bias strips by a straight line; FMODE="PLANE",
SMODE="CONSTANT" derives a single constant for the bias value;
FMODE="PLANE", SMODE="LINEAR" fits a plane to the bias-strip
data.
[CONSTANT]
-
TITLE = LITERAL (Read)
-
Title for the output image.
[Output from DEBIAS]
-
USECON = _LOGICAL (Read)
-
If TRUE then you can supply an estimate for the bias
contribution (parameter ZERO). This value is then subtracted
from the input image. Only use this option if you do not have
any bias frames or bias strips and you have good reason to
believe that the value you are supplying is accurate enough
for your purposes.
[FALSE]
-
USEEXT = _LOGICAL (Read)
-
If TRUE then certain of the parameters of this program will not
be used and the required values will be obtained from the
CCDPACK extensions of the input images instead. This method can
only be used if the images have been "imported" using the
programs PRESENT or IMPORT. Typically it is used when
processing using CCDPACK's "automated" methods (in this case
the input images should contain all the information necessary to
process them).
The parameters that this effects are:
ADC
BOUNDS
DEFERRED
DIRECTION
EXTENT
RNOISE
SATURATION
ZERO
Values obtained from the CCDPACK extension are identified in
the output log by the presence of a trailing asterisk (*).
[FALSE]
-
USESET = _LOGICAL (Read)
-
Whether to use Set header information or not. If USESET is
false then any Set header information will be ignored.
If USESET is true, then the BIAS parameter is
taken to refer to a group of files, and each IN file will
be processed using a master bias image with a Set Index
attribute which matches its own. An IN file with no Set
header is considered to match a master bias file with
no Set header, so USESET can safely be set true
when the input files contain no Set header information.
If a global value for this parameter has been set using
CCDSETUP then that value will be used.
[FALSE]
-
WMODE = LITERAL (Read)
-
The weighting method which is to be used when deriving means
or performing the least squares interpolation fits using any
bias strips. Can take the values "LINEAR", "EXP", or "NONE".
"LINEAR" and "EXP"-onential produce weights which are maximum
in the centre of each bias strip and which fall off towards
the edges. "LINEAR" weighting gives zero weighting for the
edge lines and so is the more robust.
[LINEAR]
-
ZERO = _DOUBLE (Read)
-
If USECON=TRUE then this value is subtracted from the input
image.
