% @(#)fringeccd.hlq	17.1.1.1 (ESO-SDAG) 01/25/02 17:48:53
%++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
%.COPYRIGHT  (c)  1993 European Southern Observatory
%.IDENT      fringeccd.hlq
%.AUTHOR     RHW, IPG/ESO
%.KEYWORDS   MIDAS, ccd package, FRINGE/CCD
%.PURPOSE    On-line help file for the command: FRINGE/CCD
%.VERSION    930827 RHW created
%---------------------------------------------------------------------
\se
SECTION./CCD
\es\co
FRINGE/CCD                                                       27-August-1993
\oc\su
FRINGE/CCD [in_fram] [out_fram] [fr_fram] [fr_scale]
	Do a fringe correction of the input frame
\us\pu
Purpose:    
	Do a fringe correction of the input frame
\up\sy
Syntax:     
	FRINGE/CCD [in_fram] [out_fram] [fr_fram]
\ys\pa
	in_fram =  input frame to be corrected; default is the frame stored in
                   the keyword CCD_IN.
\ap\pa
	out_fram = output frame resulting from the devision of the input frame
                   by a scaled illumination field; no default.
\ap\pa
	fr_fram  = fringe frame by which input frame is to be divided; default
                   is the frasme storedf in the keywords SC_FRFRM.
\ap\pa
        fr_scale = fringe frame scaling factor. Default is the number stored 
                   in descriptor FRINGESCALE of the fringe frame. See below.
\ap\no
Note:   
        The command devides the input frame by the flat field frame according
        to the formula:\\
                       out_fram = in_fram - fr_scale*obstimi/obstimf*fr_fram\\
        where fr_scale is the fringe scaling factor, and ostimi and obstimf 
        are the exposure time of the input and fringe frame respectively. By 
        default fringe scale factor is read from the fringe frame descriptor 
        FRINGESCALE. If no value can be obtained the default will be 1.0.
        In case the descriptor contains a number smaller or equal to zero the 
        value 1.0 will be used.\\

        In case the fringe  frame does not exit or the frame cannot be used as
        an fringe frame a fatal error will be issued.\\

        The command exists if the fringe correction was already applied.
	After the command has finished the descriptor CCDSTAT in the output 
        frame is updated to indicated that the frame is fringe corrected.
\on\see
See also:   
	SET/CCD, SHOW/CCD, REDUCE/CCD, MKFRCOR/CCD
\ees\exs
Examples:
\ex
	FRINGE/CCD susi0097 susi97frcor susi0097_fr
	Correct the frame susi0097 for fringing. The frame susi0097_fr is 
        to be used as fringe frame; output is the frame susi0097frcor.
        The fringe scaling factor will be obtained from the descriptor of the 
        fringe frame.
\xe \sxe