% @(#)flat_eche.hlq	17.1.1.1 (ESO-IPG) 01/25/02 17:50:36 
%++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
%.COPYRIGHT  (c)  1990 European Southern Observatory
%.IDENT      flat_eche.hlq
%.AUTHOR     PB, IPG/ESO
%.KEYWORDS   MIDAS, help files, FLAT/ECHELLE
%.PURPOSE    On-line help file for the command: FLAT/ECHELLE
%.VERSION    1.0  04-MAR-1991 : Creation, PB
%----------------------------------------------------------------
\se
SECTION./ECHELLE
\es\co
FLAT/ECHELLE						04-MAR-1991 PB
\oc\su
FLAT/ECHELLE [flat] [correct] [blaze]
	subtract background from flat-field image and approximate blaze profile
\us\pu
Purpose:    
            a) optionally subtract background from flat-field image
               If the descriptor BACKGROUND exists in flat-field image,
               the background step will be skipped.
               The corrected image, i.e. the flat-field corrected
               from its background, is stored as [correct]

            b) compute an approximation to the blaze profile for the 
               flat-field. The order-by-order blaze profiles are stored 
               as [blaze]

            The output images are used for flat-field correction.

            The background is approximated by spline polynomials
            fitted to points located in the interorder space.
            These points are defined by the command DEFINE/ECHELLE
            Parameters can be defaulted to the current session values,
            as displayed by SHOW/ECHELLE.
\up\sy
Syntax:     
            FLAT/ECHELLE [flat] [correct] [blaze]
\ys\pa
            flat    = flat-field image
\ap\pa
            correct = flat-field image with background subtracted
\ap\pa
            blaze   = profile of the blaze function
\ap\no
Note:       
            Default values are read from echelle keywords in sections
            2. Background and  8. Flat-Field
\on\exs
Examples:
\ex
            FLAT/ECHELLE ffima  ffcor  blaz
\xe\ex
            FLAT/ECHELLE
\xe \sxe