% @(#)offseteche.hlq	19.1 (ESO-IPG) 02/25/03 14:18:37
%++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
%.COPYRIGHT  (c)  1993 European Southern Observatory
%.IDENT      offseteche.hlq
%.AUTHOR     PB, IPG/ESO
%.KEYWORDS   MIDAS, help files, 
%.PURPOSE    On-line help file for the command: OFFSET/ECHELLE
%.VERSION    1.0  17-MAR-95 : Creation, PB
%----------------------------------------------------------------
\se
SECTION./ECHELLE
\es\co
OFFSET/ECHELLE					      17-MAR-95  PB
\oc\su
OFFSET/ECHELLE  [image] [range]  [cover]  [ordtab] [mode]
            Determines the offset along the slit between the order
            coefficients and a given echelle spectrum.
\us\pu
Purpose:    
            In reason of different positioning along the slit,
            echelle observations might present an offset with respect
            to the image used to define the order positions. The command
            OFFSET/ECHELLE determines this offset by performing a number
            of offset measurement at random positions on a raw spectrum.
\up\sy
Syntax:     
            OFFSET/ECHELLE   [image] [range]  [cover]  [ordtab] [mode]
 \\
\ys\pa
            image   = Image name (echelle spectrum at standard orientation).
                      By default the image in the display window is used
                      for offset measurement.
 \\
\ap\pa
            range   = Range of search for the offset (default 20 pixels)
 \\
\ap\pa
            cover   = Number of measurement points (default 30)
 \\
\ap\pa
            ordtab  = Name of the order table (Default: sess. keyw. ORDTAB)
 \\
\ap\pa  
            mode    = Mode of action (Verb, Silent). Default mode is 
                      Verbose in which the OFFSET keyword is set to the
                      measured offset value (the OFFSET keyword is used by
                      the EXTRACT/ECHELLE command). In mode Silent 
                      the offset value is stored in OUTPUTR(1) and the
                      OFFSET keyword is left unchanged.
 \\
\ap\sa
See also: 
            DEFINE/ECHELLE, DEFINE/HOUGH, EXTRACT/ECHELE, LOAD/ECHELLE
\as\no
Note:       
            1) The algorithm involves the measurement of the offset 
               at a number of positions selected randomly over the frame.
               Although the algorithm is robust to particle hits, it is
               possible to filter the image before processing. The signal
               to noise of the spectrum should be sufficient to allow the
               unambiguous detection of the central peak of the orders.
 \\
\on\exs
Examples:
\ex
            OFFSET/ECHELLE  value1
            Comment line
\xe\ex
            OFFSET/ECHELLE value1 value2
            Comment line
\xe \sxe




