biasbat - CCD bias-frame correction


biasbat [options] bias=file source_file ...


The biasbat program applies bias correction to a set of source frames. It means, that it subtracts the bias frame from source files and the results writes to the output file.

The source frames and also bias frame must be in FITS format and of same dimensions. The output file is in FITS format too.


The list of input files is usualy entered directly on the command line. If you are going to process a large set of files, you can use the question marks (for a single chars) or the asterisk (for a strings of chars).

The alternate way, how to process a large set of files, is the batch mode. In this mode, the list of input files is read from a given file or from the standard input. The directory file, for example named dirfile, must have the text format and the names of the input files are written on the separate lines. If the files are placed not in the current working directory, you have to specify the proper path in full or shortened form.

The mask parameters allows to set the naming of output files. The mask consists of letters, numbers and other characters allowed in the file name by the operating system. The special meaning has the question mark or the sequence of it. They will be replaced by the ordinal number of the output file, the number is always indented by leading zeros to the same number of decimal places as the number of the question marks. For example, when the mask bout????.fts is given, the output files named bout0001.fts, bout0002.fts, bout0003.fts will be generated.

The program will read the list of source files from specified file.
The program will read the list of source files from stdin.
bias=file, -bfile
Name of the bias frame file.
mask=mask, -omask
Mask of the output file(s). Default is bout????.fts.
Initial counter value. Default is 1.
Prints short help.
Prints the license.
Prints the program name and its version.
Quiet mode -- inhibits the screen printouts.
Debug mode -- extends the screen printouts.


The following command applies bias correction of 'kout0001.fts' using 'bias.fts' as correction frame. The output is written to 'bout0001.fts'.

biasbat bias=dark.fts kout0001.fts


biasbat returns a zero exist status if it succeeds to convert all specified file. Otherwise, it will stop immediately when the error occurs and returns nonzero code.


~/.cmunipack /usr/local/share/cmunipack


The project manager David Motl is also the author of the most part of the source codes. Some algorithms originates from Munipack package, coded by Filip Hroch. Algorithms for aperture photometry originates from Daophot software by P. B. Stetson. Munifind algorithm originates from Varfind tool written by Rudolf Novak and Lukas Kral.

The package uses the FITSIO library (Dr. William Pence, NASA), the FreeImage library maintained by Herve Drolon and the James Clark's EXPAT library.

The english version of the documentation was written by David Motl with great help of Petr Lutcha and Jitka Kudrnacova.


David Motl (dmotl [at]


This program is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, version 2.

This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.


airmass(1), autoflat(1), biasbat(1), cmunipack(1), biasbat(1), flatbat(1), helcor(1), kombine(1), konve(1), meanbias(1), meandark(1), munifind(1), munilist(1), munimatch(1), muniphot(1), timebat(1)