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author | Joe Hunkeler <jhunkeler@gmail.com> | 2015-08-11 16:51:37 -0400 |
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committer | Joe Hunkeler <jhunkeler@gmail.com> | 2015-08-11 16:51:37 -0400 |
commit | 40e5a5811c6ffce9b0974e93cdd927cbcf60c157 (patch) | |
tree | 4464880c571602d54f6ae114729bf62a89518057 /noao/imred/ccdred/doc/flatcombine.hlp | |
download | iraf-osx-40e5a5811c6ffce9b0974e93cdd927cbcf60c157.tar.gz |
Repatch (from linux) of OSX IRAF
Diffstat (limited to 'noao/imred/ccdred/doc/flatcombine.hlp')
-rw-r--r-- | noao/imred/ccdred/doc/flatcombine.hlp | 133 |
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diff --git a/noao/imred/ccdred/doc/flatcombine.hlp b/noao/imred/ccdred/doc/flatcombine.hlp new file mode 100644 index 00000000..549c912c --- /dev/null +++ b/noao/imred/ccdred/doc/flatcombine.hlp @@ -0,0 +1,133 @@ +.help flatcombine Aug91 noao.imred.ccdred +.ih +NAME +flatcombine -- Combine and process flat field images +.ih +USAGE +flatcombine input +.ih +PARAMETERS +.ls input +List of flat field images to combine. The \fIccdtype\fR parameter +may be used to select the flat field images from a list containing all +types of data. +.le +.ls output = "Flat" +Output flat field root image name. The subset ID is appended. +.le +.ls combine = "average" (average|median) +Type of combining operation performed on the final set of pixels (after +rejection). The choices are +"average" or "median". The median uses the average of the two central +values when the number of pixels is even. +.le +.ls reject = "avsigclip" (none|minmax|ccdclip|crreject|sigclip|avsigclip|pclip) +Type of rejection operation. See \fBcombine\fR for details. +.le +.ls ccdtype = "flat" +CCD image type to combine. If no image type is given then all input images +are combined. +.le +.ls process = yes +Process the input images before combining? +.le +.ls subsets = yes +Combine images by subset parameter? If yes then the input images are +grouped by subset parameter and each group combined into a separate output +image. The subset identifier is appended to the output and sigma image +names. See \fBsubsets\fR for more on the subset parameter. This is generally +used with flat field images. +.le +.ls delete = no +Delete input images after combining? Only those images combined are deleted. +.le +.ls clobber = no +Clobber existing output images? +.le +.ls scale = "mode" (none|mode|median|mean|exposure) +Multiplicative image scaling to be applied. The choices are none, scale +by the mode, median, or mean of the specified statistics section, or scale +by the exposure time given in the image header. +.le +.ls statsec = "" +Section of images to use in computing image statistics for scaling. +If no section is given then the entire region of the image is +sampled (for efficiency the images are sampled if they are big enough). +.le + +.ce +Algorithm Parameters +.ls nlow = 1, nhigh = 1 (minmax) +The number of low and high pixels to be rejected by the "minmax" algorithm. +.le +.ls nkeep = 1 +The minimum number of pixels to retain or the maximum number to reject +when using the clipping algorithms (ccdclip, crreject, sigclip, +avsigclip, or pclip). When given as a positive value this is the minimum +number to keep. When given as a negative value the absolute value is +the maximum number to reject. This is actually converted to a number +to keep by adding it to the number of images. +.le +.ls mclip = yes (ccdclip, crreject, sigclip, avsigcliip) +Use the median as the estimate for the true intensity rather than the +average with high and low values excluded in the "ccdclip", "crreject", +"sigclip", and "avsigclip" algorithms? The median is a better estimator +in the presence of data which one wants to reject than the average. +However, computing the median is slower than the average. +.le +.ls lsigma = 3., hsigma = 3. (ccdclip, crreject, sigclip, avsigclip, pclip) +Low and high sigma clipping factors for the "ccdclip", "crreject", "sigclip", +"avsigclip", and "pclip" algorithms. They multiply a "sigma" factor +produced by the algorithm to select a point below and above the average or +median value for rejecting pixels. The lower sigma is ignored for the +"crreject" algorithm. +.le +.ls rdnoise = "0.", gain = "1.", snoise = "0." (ccdclip, crreject) +CCD readout noise in electrons, gain in electrons/DN, and sensitivity noise +as a fraction. These parameters are used with the "ccdclip" and "crreject" +algorithms. The values may be either numeric or an image header keyword +which contains the value. +.le +.ls pclip = -0.5 (pclip) +Percentile clipping algorithm parameter. If greater than +one in absolute value then it specifies a number of pixels above or +below the median to use for computing the clipping sigma. If less +than one in absolute value then it specifies the fraction of the pixels +above or below the median to use. A positive value selects a point +above the median and a negative value selects a point below the median. +The default of -0.5 selects approximately the quartile point. +See \fBcombine\fR for further details. +.le +.ls blank = 1. +Output value to be used when there are no pixels. +.le +.ih +DESCRIPTION +The flat field images in the input image list are combined. If there +is more than one subset (such as a filter or grating) then the input +flat field images are grouped by subset and an combined separately. +The input images may be processed first if desired. However if all +zero level bias effects are linear then this is not necessary and some +processing time may be saved. The original images may be deleted +automatically if desired. The output pixel datatype will be real. + +This task is a script which applies \fBccdproc\fR and \fBcombine\fR. The +parameters and combining algorithms are described in detail in the help for +\fBcombine\fR. This script has default parameters specifically set for +flat field images and simplifies the combining parameters. There are other +combining options not included in this task. For these additional +features, such as thresholding, offseting, masking, and projecting, use +\fBcombine\fR. +.ih +EXAMPLES +1. The image data contains four flat field images for three filters. +To automatically select them and combine them as a background job +using the default combining algorithm: + + cl> flatcombine ccd*.imh& + +The final images are "FlatV", "FlatB", and "FlatR". +.ih +SEE ALSO +ccdproc, combine, subsets +.endhelp |