% @(#)frcor_ccd.hlq	17.1.1.1 (ESO-IPG) 01/25/02 17:48:53
%++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
%.COPYRIGHT  (c)  1993 European Southern Observatory
%.IDENT      frcor_ccd.hlq
%.AUTHOR     RHW, IPG/ESO
%.KEYWORDS   MIDAS, ccd package, FRCOR/CCD
%.PURPOSE    On-line help file for the command: FRCOR/CCD
%.VERSION    930827 RHW Documentation created
%---------------------------------------------------------------------
\se
SECTION./CCD
\es\co
FRCOR/CCD                                                       20-Dec-1993 RHW
\oc\su
FRCOR/CCD [in_spec] [out_frm] [xboxmn,xboxmx] [yboxmn,yboxmx] [clip] 
           [lowsig,higsig]
	Make fringe correction frame(s0 from sky frames
\us\pu
Purpose: 
	Make fringe correction frame(s0 from sky frames
\up\sy
Syntax:     
        FRCOR/CCD [in_spec] [out_frm] [xboxmn,xboxmx] [yboxmn,yboxmx]
                   [clip] [lowsig,higsig]
\ys\pa
        in_spec = single frame or MIDAS CCD reduction table (with extension 
                  .tbl) containing the names of the sky frames from which the 
                  fringe correction frames should be created. In case 
                  the input is a reduction table the names of the input frames
                  will be obtained from the column :SKY in that table (see 
                  below). Default input is taken from the keyword CCD_IN.
\ap\pa
        out_frm = name of the output fringe correction frame. Default output is
                  taken from the keyword CCD_OUT. This parameter is only used 
                  is case of single frame input for the first parameter. In 
                  case the input is a ccd reduction table the name(s) of the 
                  output frame(s) will be read from tke column :FR in this 
                  table (see below). 
\ap\pa  
        xboxmn,xboxmx = minimum and maximum smoothing box size along the x 
                  axes.  The minimum box size is used at the edges and grows 
                  to the maximum size in the middle of the image.  This 
                  allows the smoothed image to better represent gradients 
                  at the edge of the image. If a size is less then 1 it is 
                  interpreted as a fraction of the image size. If a size is
                  greater than or equal to 1 then it is the box size in 
                  pixels.  A size greater than the size of image selects a 
                  box equal to the size of the image. Default values are taken
                  from the keyword IL_XBOX.
\ap\pa
        yboxmn,yboxmx = see above. Default values are taken from IL_YBOX.
\ap\pa
        clip =    Clean the input frame(s) of objects? If yes then a clipping 
                  algorithm is used to detect and exclude objects from the 
                  smoothing. Default taken from IL_CLIP.
\ap\pa
        lowsig,higgsig = sigma clipping thresholds above and below the smoothed
                  sky illumination frame. Default values are taken from the 
                  keyword IL_SIGMA. The keyword is only read in case clip=yes.
\ap\no
Note:     
        The input sky frames are automatically processed up through flat 
        fielding and illumination before computing the fringe pattern. 

        In case the input is the CCD reduction table the command will create 
        fringe correction frames for all selected data sets (flat frames)
        in  the reduction table, provided the sky column (:SKY) contains 
        existing sky frames. The name of the output illumination frames are 
        obtained from the column :FR. Relevant calibration frame will be taken
        from the other calibration column belonging to the same data set.\\

        The effects of objects in the sky frames may be minimized by using a 
        sigma clipping algorithm to detect and exclude the objects from the 
        average. 

        The command operates very similar to the command REDUCE/CCD, which
        the exception that it does not check for the exposure type of the
        input frame. Master frames to be used to calibrate the input frame
        first are taken for the SC_ keywords (in case of single frame input),
        or from the reduction table in case of table input. For details see
        the command REDUCE/CCD. \\

        The calibrated sky frame is heavily smoothing to obtain the sky 
        illumination frame using a moving "boxcar" average. This smoothed 
        frame is subtracted from the unsmoothed frame to yield the output 
        fringe frame. The fringe frame can used by REDUCE/CCD to remove the 
        fringe pattern from the science frames.\\

        For more information see the CCD chapter in Volume B of the User's 
        manual.
\on\see
See also:   
        SET/CCD, SHOW/CCD, HELP/CCD, REDUCE/CCD, ILLSKY/CCD
\ees\exs
Examples:
\ex
        FRCOR/CCD redtbl.tbl
        Reduce all flat frames in the flay field column in the ccd reduction
        table redtbl.tbl. Master calibration frames will be obtained from that
        reduction table. Do the calibration according to the keyword settings.
        After the calibrations are done create the fringe frames, using the 
        `IL_' and `FR_' keyword settings. Calibration frames will be taken from
        the table redtbl.tbl
\xe\ex
        FRCOR/CCD m100rraw m100rraw_fr
        Start the ccd reduction sequence for the frame m100rraw. This input 
        frame should be present. The output frame will be m100rraw_fr. In case
        only dark correction is to be applied the names of this calibration 
        frame will be obtained from the keyword SC_DKFRM.
\xe\sxe