% @(#)dark_ccd.hlq	17.1.1.1 (ESO-SDAG) 01/25/02 17:48:53
%++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
%.COPYRIGHT  (c)  1993 European Southern Observatory
%.IDENT      dark_ccd.hlq
%.AUTHOR     RHW, IPG/ESO
%.KEYWORDS   MIDAS, ccd package, DARK/CCD
%.PURPOSE    On-line help file for the command: DARK/CCD
%.VERSION    930329 RHW created
%---------------------------------------------------------------------
\se
SECTION./CCD
\es\co
DARK/CCD                                                        29-Mar-1993 RHW
\oc\su
DARK/CCD [in_fram] [out_fram] [dk_fram]
	Correct input frame for dark current offset using a dark current frame
\us\pu
Purpose:    
	Correct input frame for dark current offset using a dark current frame
\up\sy
Syntax:     
	DARK/CCD [in_fram] [out_fram] [dk_fram]
\ys\pa
	in_fram =  input frame to be corrected; default is the name stored in
                   the keyword CCD_IN.
\ap\pa
	out_fram = output frame resulting from the weighted subtracting of 
                   the dark frame from the input frame; no default
\ap\pa
	dk_fram  = dark frame to be subtracted from input frame; default is 
                   the name stored in the keyword SC_DKFRM.
\ap\no
Note:   
        The command subtracts the scaled dark current frame from the input
        frame. The scaling factor is O_TIME1/O_TIME2, where O_TIME1 is the 
        exposure time of the input frame, and O_TIME2 is the exposure time of 
        the dark current frame.\\

        In case the dark frame does not exit, a fatal error will be issued. In 
        such case you may generate the bias frame using COMBINE/CCD.\\

        Both, the input and dark current frame should contain the descriptors 
        for the exposure time (see keyword `O_DESCR' for the actual name of the
        descriptor. If they are non-existing or contain invalid values (less 
        or equal to zero) an error message is given and an exist follows.\\

        The command will exit if the dark correction has already been done.
	After the command has finished the descriptor CCDSTAT in the output 
        frame is updated to indicated that the dark has been subtracted.
\on\see
See also:   
	SET/CCD, SHOW/CCD, COMBINE/CCD, REDUCE/CCD, COMPUTE/IMAGE
\ees\exs
Examples:
\ex
	DARK/CCD susi0097 susi97dkcor susidark
	Subtract the dark frame `susidark' from the input frame susibs0097.
	The output frame is susi97dkcor.
\xe \sxe