II-1. Biases.
To combine the biases use "zerocombine". Our experience is that
the bias structure does not drift during a run.
ccdproc zero* xtalk+ over+ rim+ fixpix+ zeroc- darkc- flatc- xtalkf="xtalkphil.dat" function=spline3 order=3900
zerocombine zero* Zerona.fits
Where the parameters for zerocombine are:
PACKAGE = mscred
TASK = zerocombine
input = @Z List of zero level images to combine
(output = Zerona_Feb.fits) Output zero level name
(combine= average) Type of combine operation
(reject = minmax) Type of rejection
(ccdtype= zero) CCD image type to combine
(process= yes) Process images before combining?
(delete = no) Delete input images after combining?
(scale = none) Image scaling
(statsec= ) Image section for computing statistics
(nlow = 0) minmax: Number of low pixels to reject
(nhigh = 1) minmax: Number of high pixels to reject
(nkeep = 1) Minimum to keep (pos) or maximum to reject
(mclip = yes) Use median in sigma clipping algorithms?
(lsigma = 3.) Lower sigma clipping factor
(hsigma = 3.) Upper sigma clipping factor
(rdnoise= 0.) ccdclip: CCD readout noise (electrons)
(gain = 1.) ccdclip: CCD gain (electrons/DN)
(snoise = 0.) ccdclip: Sensitivity noise (fraction)
(pclip = -0.5) pclip: Percentile clipping parameter
(blank = 0.) Value if there are no pixels
(mode = ql)