masterbias

NAME

masterbias -- create a masterbias image


USAGE

masterbias [flags] bias-images

nan n -1e10
outfile o masterbias.fits
reg r 2050:2165,5:2045
tresh t 8000.0
verbose v 0


PARAMETERS

nan = -1e10
Not a number value. Pixels with this value are not taken into account. Also all pixels in the output masterbias and errorframe where a value could not be calculated are set to "nan".
outfile = "masterbias.fits"
Output masterbias filename.
reg = 2050:2165,5:2045
Overscan region. The statistics in this region (median, sigma) are printed and the median of the region is being subtracted from each image before combination. If the region is 0:0,0:0 the whole image is taken.
tresh = 8000.0
All pixels with a higher value than this upper treshold are not taken into account.
verbose = 0
Verbose level. If verbose >= 1, an additional output image is craeted containing the individual number of combined images for each pixel.
bias-images
Single bias-images to be combined. At least 2 images have to be specified.

DESCRIPTION

The task masterbias creates a masterbias image out of a given set of at least 2 single bias images. First the constant bias offset is measured in the overscan region specified by the reg-flag and subtracted from each of the input images. Pixels with a value higher than tresh or a value of nan are masked and not taken into account. The median, its standard deviation and the number of used pixel is printed. After that the masterbias is calculated pixel by pixel according to the following rules: If a certain pixel is masked in all but one of the input images the pixel in the output image is set to the value in the remaining frame and the corresponding pixel in the output errorframe is set to "nan". If a certain pixel is valid in 2-10 images the pixel in the output image is set to the median. If there are more than 10 valid pixels the value is calculated in an iterativ kappa-sigma-clipping process where in each step an average and sigma is calculated and than for the next step all 3-sigma outliers are clipped. The finaly taken number of pixels is stored in the "u.masterbias" output image.
If verbose >= 1, an additional output image is craeted containing the individual number of combined images for each pixel.


OUTPUT

masterbias.fits
output masterbias image
e.masterbias.fits
errorframe of masterbias image

If verbose >= 1:
u.masterbias.fits
this image contains the individual number of combined images for each pixel

EXAMPLE

masterbias -o masterbias_040809.fits bia___040809_*.fits


Task index
This task was implemented by A. Riffeser
Dokumentation maintained by J. Koppenhöfer
This file was last time updated on 22 Feb 2005