% @(#)calibrlong.hlq	17.1.1.1 (ESO-IPG) 01/25/02 17:53:23
%++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
%.COPYRIGHT  (c)  1993 European Southern Observatory
%.IDENT      calibrlong.hlq
%.AUTHOR     23-MAR-93, IPG/ESO
%.KEYWORDS   MIDAS, help files, 
%.PURPOSE    On-line help file for the command: CALIBRATE/LONG
%.VERSION    1.0  PB : Creation, 23-MAR-93
%----------------------------------------------------------------
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SECTION./LONG
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CALIBRATE/LONG					   PB  20-APR-94
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CALIBRATE/LONG  [tol]  [deg]  [mtd]  [guess]
	Wavelength calibration of 1D and long-slit spectra
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Purpose:    
            Precise purpose of the command
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Syntax:
            CALIBRATE/LONG  [tol]  [deg]  [mtd]  [guess]
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            tol    = tolerance for rejection of outliers.
                     If tol > 0, value is assumed to be in pixel units
                     If tol < 0, value is assumed to be in wavelength units.\\
                     Session keyword: TOL; default: 0.2
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            deg    = Degree of the bivariate polynomial fitted to the 
                     dispersion relation. This relation is computed only if 
                     the session keyword TWODOPT is set to YES. \\
                     Session keyword: DCX; default: 3,1 \\
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            mtd    = mode of operation as IDENT (default), GUESS or LINEAR.
                     In mode IDENT, the command IDENT/LONG must have been used 
                     previously. In mode GUESS, a calibrated session must have
                     been saved by command SAVE/LONG. The mode LINEAR must
                     be used after the command ESTIMATE/DISPERSION. This  
                     command avoids the interactive identification of lines. \\
                     Session keyword: WLCMTD; default: IDENT
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            guess  = name of reference session, as used in command SAVE/LONG. 
                     This parameter is required if mtd=GUESS. Default is the 
                     current line table defined by the keyword LINTAB. \\
                     Session keyword: GUESS; no default value. 
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See also: 
            SEARCH/LONG, IDENT/LONG, ESTIMATE/DISPERSION, PLOT/RESIDUAL, 
            PLOT/IDENT, PLOT/DISTORTION
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Note:       
            1) The spectrum must be such that the dispersion dispersion
               is parallel to the rows of the image and the wavelength
               must be increasing from the left to the right. Start and
               step descriptors of the spectrum should preferably be set
               to 1,1.

            2) Parameters relative to this command are displayed by
               SHO/LONG W

            3) The following session keywords are involved in the
               wavelength calibration process:
               TOL, DCX, LINTAB, LINCAT, IMIN, WLCMTD, ALPHA, WLCNITER,
               COERBR, YSTART, GUESS, MAXDEV, SHIFT, COROPT, CORVISU,
               TWODOPT, START, STEP, WSTART, WEND, WSTEP.

            4) Only the keywords TOL, DCX, WLCMTD, GUESS can be provided
               on the command line. All other keywords must be set with the
               command SET/LONG.

            5) Session keywords WSTART, WEND, WSTEP are initialised at 
               the end of the calibration process. These values are
               displayed by SHO/LONG R.

            The dispersion relation is modelled independently for each
            row by a 1D polynomial. Interactive line identification has to be
            previously performed by command IDENT/LONG, on the row YSTART
            of the calibration image,  which stores the identifications
            in table LINE  generated by SEARCH/LONG.\\

            Line matching in a  line catalogue is then enabled in
            order to identify  as many lines as possible and the dispersion
            coefficients are calculated for the row YSTART. The process
            goes then to the bottom and the top of the frame and uses
            the dispersion coefficients of each row to compute a guess
            for the line identifications of the following one.

            The following session parameters are used:\\
               YSTART: row on which the interactive line identification
                       has been done\\
               DCX(1): degree of the 1D polynomial\\
               LINCAT: reference catalogue with comparison lines\\
               TOL   : tolerance window to assign the wavelength identification
                       to a given line position.

            The resulting dispersion coefficients are stored in a table
            which name is stored in the keyword COERBR (default: coerbr.tbl).
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Examples:
\ex
            CALIBRATE/LONG \\
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            CALIBRATE/LONG deg=2,2  tol=-0.1 \\
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