% @(#)extraceche.hlq	17.1.1.1 (ESO-IPG) 01/25/02 17:50:36 
%++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
%.COPYRIGHT  (c)  1990 European Southern Observatory
%.IDENT      extraceche.hlq
%.AUTHOR     PB, IPG/ESO
%.KEYWORDS   MIDAS, help files, EXTRACT/ECHELLE
%.PURPOSE    On-line help file for the command: EXTRACT/ECHELLE
%.VERSION    1.0  17-DEC-1986 : Creation, JDP
%----------------------------------------------------------------
\se
SECTION./ECHE
\es\co
EXTRACT/ECHELLE						28-NOV-1991 PB
\oc\su
EXTR/ECH input output [params] [method]
	extract echelle orders
\us\pu
Purpose:    
            Extract echelle orders. Position of the orders are defined
            in the auxiliary table order.tbl, generated by the command
            DEFINE/ECHELLE or DEFINE/HOUGH. The command call low level
            commands EXTRACT/ORDER or EXTRACT/OPTIMAL.
\up\sy
Syntax:     EXTRACT/ECHELLE input output [params] [method]
\ys\pa
            input   = input image sampled in the usual pixel-pixel space
\ap\pa
            output  = extracted image sampled in the space pixel-order
\ap\pa
            params  = extraction parameters, depending on the method: \\
                      method LINEAR or AVERAGE: slit,offset
                      method OPTIMAL:           slit,ron,gain,sigma.
\ap\pa
            slit    = slit length in pixels \\
                      The slit length must be slightly larger than the
                      order to avoid periodic ripple due to the inclination
                      of the orders. However, a slit much larger than
                      the order will introduce interorder noise in
                      the spectrum.
\\
                      Echelle keyword is SLIT. 
\ap\pa
            offset  = offset in pixels of the center of the slit with respect
                      to the position defined by the coefficients in the
                      table order.tbl.
\\
                      The offset is positive if the central line of the order
                      is above the trace displayed by LOAD/ECHELLE.
\\
                      Echelle keyword is OFFSET.
\ap\pa
            ron,g,sigma = read-out-noise(e-), inverse gain factor (e-/ADU),
                      threshold (in units of the theoretical noise
                      sigma of each pixel). See also the help file of
                      command EXTRACT/OPTIMAL.
\\
                      If not provided on the command line, these values
                      are read from echelle keywords RON, GAIN, EXTSIGMA.
\ap\pa
            method  = extraction method to define the way to compute the
                      pixel values of the numerical slit as: \\
                LINEAR            linear interpolation (default)
                AVERAGE           linear interpolation and average
                OPTIMAL           optimal extraction.
\\
                      Echelle keyword is EXTMTD.
\ap\no
Note:       The command DEFINE/ECHELLE or DEFINE/HOUGH 
             has to be used previously.

\on\exs
Examples:
\ex
            EXTRACT/ECHELLE   raw   extract   6
\xe \sxe