% @(#)extracsky.hlq	17.1.1.1 (ESO-IPG) 01/25/02 17:50:36
%++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
%.COPYRIGHT  (c)  19943 European Southern Observatory
%.IDENT      extracsky.hlq
%.AUTHOR     PB, IPG/ESO
%.KEYWORDS   MIDAS, help files, 
%.PURPOSE    On-line help file for the command: EXTRACT/SKY
%.VERSION    1.0  07-OCT-94 : Creation, PB
%----------------------------------------------------------------
\se
SECTION./SKY
\es\co
EXTRACT/SKY					      10-OCT-94  PB
\oc\su
EXTRACT/SKY  in out [mode]
	Extracts sky spectrum.
\us\pu
Purpose:    
            The limits of the sky windows must have been defined
            with DEFINE/SKY. An extracted sky spectrum is provided,
            similar to extracted echelle spectra.
\up\sy
Syntax:     
            EXTRACT/SKY  in out  [mode]
 \\
\ys\pa
            in  = Name of input spectrum. 
 \\
\ap\pa
            out = Name of output extracted spectrum. This is
                  a 2D image in pixel-order space similar to the
                  one produced by the command EXTRACT/ECHELLE.
 \\
\ap\pa
            mode = AVERAGE or FILTER. In mode Average, the sky windows
                   are simply averaged. In mode Filter, each sky
                   window is subdivided in three and the maximum 
                   pixel is  rejected to eliminate particle hits.
                   For one sky window one out of three pixel is 
                   rejected. With two sky windows, two out of six 
                   pixels are rejected.
                   
\ap\sa
See also: 
            DEFINE/SKY, EXTRACT/ECHELLE, DEFINE/ECHELLE, DEFINE/HOUGH
\as\no
Note:       
            1) A preliminary definition of the orders with DEFINE/ECHE
               or DEFINE/HOUGH and of the sky windows with DEFINE/SKY
               is required.
 \\
\on\exs
Examples:
\ex
            EXTRACT/SKY  rot0002  sky2
\xe \sxe