package: CCD image reduction package

Package: ccdred

Usage

ccdred

Parameters

pixeltype = "real real"

Output pixel datatype and calculation datatype. When images are processed or created the output pixel datatype is determined by this parameter if the specified datatype is of equal or higher precision otherwise the input image datatype is preserved. For example if the output datatype is specified as "input" then input images which are "short" or "ushort" will be output as integer but any real datatype input images will remain real. The allowed types and order of precision are "short", "ushort", "int", "long", "real", or "double", for short signed integer, short unsigned integer, integer, long integers, and real or double floating point. Note that if short input images are processed into real images the disk space required will generally increase. The calculation datatypes may only be short and real with a default of real if none is specified.

verbose = no

Print log information to the standard output?

logfile = "logfile"

Text log file. If no filename is specified then no log file is kept.

plotfile = ""

Log metacode plot file for the overscan bias vector fits. If no filename is specified then no metacode plot file is kept.

backup = ""

Backup prefix for backup images. If no prefix is specified then no backup images are kept when processing. If specified then the backup image has the specified prefix.

instrument = ""

CCD instrument translation file. This is usually set with setinstrument.

ssfile = "subsets"

Subset translation file used to define the subset identifier. See subsets for more.

graphics = "stdgraph"

Interactive graphics output device when fitting the overscan bias vector.

cursor = ""

Graphics cursor input. The default is the standard graphics cursor.

version = "June 1987"

Package version.

Description

The CCD reduction package is loaded when this command is entered. The package contains parameters which affect the operation of the tasks it defines. When images are processed or new image are created the output pixel datatype is that specified by the parameter pixeltype. Note that CCD processing replaces the original image by the processed image so the pixel type of the CCD images may change during processing. The output pixel type is not allowed to change to a lower precision but it is common for input short images to be processed to real images. Processing images from short to real pixel datatypes will generally increase the amount of disk space required (a factor of 2 on most computers).

The tasks produce log output which may be printed on the standard output (the terminal unless redirected) and appended to a file. The parameter verbose determines whether processing information is printed. This may be desirable initially, but when using background jobs the verbose output should be turned off. The user may look at the end of the log file (for example with tail) to determine the status of the processing.

The package was designed to work with data from many different observatories and instruments. In order to accomplish this an instrument translation file is used to define a mapping between the package parameters and the particular image header format. The instrument translation file is specified to the package by the parameter instrument. This parameter is generally set by the task setinstrument. The other file used is a subset file. This is generally created and maintained by the package and the user need not do anything. For more sophisticated users see instruments and subsets.

The package has very little graphics output. The exception is the overscan bias subtraction. The bias vector is logged in the metacode plot file if given. The plot file may be examined with the tasks in the plot package such as gkimosaic. When interactively fitting the overscan vector the graphics input and output devices must be specified. The defaults should apply in most cases.

Because processing replaces the input image by the processed image it may be desired to save the original image. This may be done by specifying a backup prefix with the parameter backup. For example, if the prefix is "orig" and the image is "ccd001", the backup image will be "origccd001". The prefix may be a directory but it must end with '/' or '$' (for logical directories).

See also

ccdproc, instruments, setinstrument, subsets