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			       RF

      REFCENT is a module which corrects a two-dimensional spectrum for the
 effects of differential refraction in the atmosphere.  Each column of data is
 shifted vertically by means of a tapered sinc interpolation.  The amount of 
 shift is calculated from the zenith distance of the observation, the 
 orientation of the slit relative to the horizon, and a model for the 
 refractive index (7th order fit to parameters in Allen's "Astrophysical 
 Quantities").  Because this module requires a lot of cpu time, it is best 
 to run it as a batch job.

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 Enter an option:                              21-MAR-1989 11:32:06.52
 OPTION=RF  
 REFCENT, Version 4
 Open the file of spectral data for which atmospheric dispersion effects
 are to be removed:
 Enter the filename:  (<CR> for default)
 FILE=LONG
 There is one map in the file
 Reading from the file
   10 rows of  576 pixels in R4 format
 Enter the effective wavelength at which the guiding was done:
 (units of Angstroms)
 WAVELENGTH=5700
 Enter the scale along the slit:  (arc seconds/pixel)
 SCALE=.63
 Enter the position angle of the slit on the sky:  (degrees E of N)
 POSITION_ANGLE=15
 Is the horizon toward the low row side of the slit?  (default = Y)
 LOW=
 T
 Enter a choice:
      H = Latitude, declination, and hour angle
          from SAD header information
      M = Manual input of above quantities (default)
  
 CHOICE=M
 Enter the latitude in degrees, minutes, and seconds:
 LATITUDE=32 0 0
 Enter the declination in degrees, minutes, and seconds:
 DECLINATION=47 22 01
 Enter the hour angle in hours, minutes, and seconds:  (East < 0)
 HOUR_ANGLE=-2 03 40
 Open a file for the shifted data
 NMAPS=    1 NPLNS=    1 NROWS=    10 NELS=   576
 Enter the filename:  (<CR> for default)
 FILE=LONGNEW
 Creating new file
 Do you wish to copy the header from the input to output file?  (default = Y)
 SAME=
 T
 Maximum shift was:     -2.74 pixels at   4500.00  Angstroms

 		If the file contains several maps, after doing the first
 		map, use option DO, e.g., OPTION=DO($=2:11).RF(MAPI=$,MAPO=$)
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