*imcontour* - Iso-intensity contour map

The contours can be displayed in sky or pixel coordinates. The scale defaults to include the whole field, and is in arcsec/mm (sky grid) or pixel/mm (pixel grid). The user can change the plot scale by manually resetting the (hidden) parameter, ``scale''.

input file: rp90_ab_smo.imh

  xr> xplot 
  xp> imcontour   
  IRAF image filename: rp90_ab_smo 
  Grid type  (sky|pixel) : sky      # sky coordinates will be read from the header 
  Units (pixel|peak|sigma):  pixel                # pixel countour levels in counts 
                                                                  # per image pixel 
                                   # peak --> contour levels as % of peak intensity 
                    # sigma --> contour levels as S/N ratio (with error array only) 
  Contour Levels: 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9

The result will appear in the graphics window (see Figure 6.1). If you are using Xwindows, you are now in cursor mode:

Figure 6.1: Output of the tasks ``imsmooth'' & ``imcontour''. this is an off-center point source and the assymmetry is due to coma caused by the optics. This is exactly the example used in Section 6.4.

  =  sends a snapshot of the current graph to the printer.
  q  exits from graphic mode.

  xp> =gcur   to re-enter cursor mode

Alternatively contours can be specified logarithmically and using a range:

  xs> imcontour 
  IRAF image filename: rp90_ab_smo 
  Grid type:  sky 
  Units (pixel|peak|sigma): peak 
  Contour Levels:  log 5 90 8              # 9 logarithmic contours in the interval 
                                                 # from 5% to 90% of the peak value

To send a contour plot directly to the printer, set the plot output device.

  xs> imcontour.device=stdplot                            # Directly to the printer
                                                # nothing will appear on the screen

then run imcontour as above examples. If hardcopy does not appear type:

  xs> gflush

N.B.: In imcontour, leaving the parameter isystem blank will read and use the coordinate system from the header. Problems will arise if isystem is given as one coordinate system and the .imh header is another coordinate system.