masterbias -- create a masterbias image
masterbias [flags] bias-images
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.
masterbias -o masterbias_040809.fits bia___040809_*.fits