% @(#)estimadisp.hlq	19.1 (ESO-IPG) 02/25/03 14:24:03
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%.COPYRIGHT  (c)  1993 European Southern Observatory
%.IDENT      estimadisp.hlq
%.AUTHOR     11-APR-93, IPG/ESO
%.KEYWORDS   MIDAS, help files, 
%.PURPOSE    On-line help file for the command: ESTIMATE/DISPERSION
%.VERSION    1.0  PB : Creation, 11-APR-93
%----------------------------------------------------------------
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SECTION./DISPERSION
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ESTIMATE/DISPERSION					   PB  11-APR-93
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ESTIMATE/DISPERSION  wdisp  wcent  [ystart]  [line]  [cat]
	Estimate a linear approximation of the dispersion relation
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Purpose:    
            Using an approximate definition of the central wavelength
            and average dispersion, the command provides a better 
            estimate of the linear model, allowing to start the 
            command CALIBRATE/LONG in mode WLCMTD=LINEAR. This new
            command is provided on an experimental basis. Any
            feedback is appreciated.
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Syntax:     
            ESTIMATE/DISPERSION  wdisp  wcent  [ystart]  [line]  [cat]
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            wdisp  = dispersion,tol,acc. The dispersion is provided in
                     wavelength units per pixel. The tolerance and the
                     accuracy are in percent (Defaults: 30\%, 1\%).
\ap\pa
            wcent  = central wavelength,tol,acc. The central wavelength
                     is in wavelength units (same units as in the line
                     catalog LINCAT). Tolerance and accuracy are in 
                     pixels. (Defaults: 100, 1).
\ap\pa
            ystart = Starting row, in pixels. The value is automatically 
                     set to the central row number if YSTART = 0  \\
                     Session keyword: YSTART; default: 0 
\ap\pa
            line   = Name of the line table. \\
                     Session keyword: LINTAB; default: line.tbl
\ap\pa
            line   = Name of the line catalog. \\
                     Session keyword: LINCAT; no default value.
\ap\sa
See also: 
            SEARCH/LONG, CALIBRATE/LONG
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Note:       
            1) Since the method is based on a linear model of the
            dispersion relation, the results can be inaccurate if the
            dispersion relation presents an important error of linearity.
            This is normally the case with the Boller and Chivens 
            spectrograph.
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Examples:
\ex
            ESTIMATE/DISPERSION  wcent=5200 wdisp=2.1
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