MKBIAS

Name

mkbias

Purpose

Collect and combine CCD bias frames into a superbias frame

Description

The files are assumed to be named as 'root'NNN where 'root' is the
root of the file name that you supply and NNN is a three digit number.
If your file name has an imbedded '.' then add it to the root.
The specified range of files are all read in from FITS files. Then each
image has the overscan mean subtracted (if desired), cropped (as indicated).
These images are then averaged. The averaging is done with AVGCLIP.PRO
which does a robust average of the image stack so that cosmic rays or
other transient image defects are eliminated.
When done, the resulting bias image is returned to the caller and the image
is saved to a FITS file with the specified output filename.

Calling Sequence

mkbias,root,outsuf,start,nframes,bias,good

Inputs

root - Root of the file name (you must include . in the name).
outsuf - The suffix of the final output file.
start - First frame number to read (integer or long).
Start can also be a vector of explicit frame numbers to load.
In this case, nframes need not be specified and in fact will
be ignored.
Additionally, start can also be a string array containing the
file names of all files to be read. In this case, set nframes
to 0 or someother innocuous integer. Exclude is treated
differently. In this case, exclude is a vector of the same
length as start and is 0 if the file is to be used, 1 if not.
nframes - Number of frames to average.

Optional Input Parameters

Keyword Input Parameters

CROP = region of original image to save, default=no cropping.
[x1,x2,y1,y2]
DIGITS - Optional input to indicate how many digits are in the suffix
of the file name. The default for this input is 0. In this
case it uses the ROBOCCD scheme which is three digits up
to 999. After that, it gets complicated, see numtoflist
for more information. If you were to give it a value of
three you would get the same behavior except you won't get
the ROBOCDD extension. This is really designed for when
you have four or more digits.
DDIR = Directory to look for raw data in. Default = ''
EXCLUDE - Optional vector of image numbers that should be excluded from
average. Default is to include all frames.
OVERSCAN = column overscan region to use for frame bias level,
default=no overscan subtraction.
RDNOISE - Read noise of CCD [in DN], default=10
MINGOOD - Minimum number of frames required to be considered a good
bias. (Default=15)
MAXBAD - Maximum number of bad rows allowed per image (see gradebias)
Default is inherited from gradebias

Outputs

bias - Final robust averaged/cropped bias image.
good - Flag, true if this collection of bias images is considered to be
good.

Keyword Output Parameters

Common Blocks

Side Effects

Restrictions

Procedure

Modification History

95/03/09 - Initial crude version written, Marc W. Buie, Lowell Observatory
95/06/13, MWB, added OVERSCAN and CROP keywords
95/11/22, MWB, add EXCLUDE keyword
2000/02/02, MWB, rewrite to add support for multigroup FITS files.
2000/02/28, MWB, added support for frame numbers > 999.
2001/02/23, MWB, added option to provide input file list.
2001/04/28, MWB, added DDIR keyword.
2005/01/04, MWB, changed so .fits tag can come and go in file names.
2006/07/14, MWB, added RDNOISE keyword
2006/10/23, MWB, fixed output header keyword problem (remove BSCALE/BZERO)
2007/06/20, MWB, fixed minor bug with image list for start
2015/04/26, MWB, added tool to provide a quality grade for set of images
2015/05/03, MWB, added much more sophisticated logic to build the superbias.
Automatic filtering of bad frames is done internally.
2016/05/29, MWB, added DIGITS keyword