IMCONTOUR

       Make a contour plot labeled with astronomical coordinates.

       The type of coordinate display is controlled by the keyword TYPE
       Set TYPE=0 (default) to measure distances from the center of the image
       (IMCONTOUR will decide whether the plotting units will be in
       arc seconds, arc minutes, or degrees depending on image size.)
       Set /TYPE for standard RA and Dec labeling
       By using the /NODATA keyword, IMCONTOUR can also be used to simply
       provide astronomical labeling of a previously displayed image.

       IMCONTOUR, im, hdr,[ /TYPE, /PUTINFO, XDELTA = , YDELTA =, _EXTRA =
                            XMID=, YMID= ]

       IM - 2-dimensional image array
       HDR - FITS header associated with IM, string array, must include
               astrometry keywords.   IMCONTOUR will also look for the
               OBJECT and IMAGE keywords, and print these if found and the
               PUTINFO keyword is set.

       /TYPE - the type of astronomical labeling to be displayed.   Either set
               TYPE = 0 (default), distance to center of the image is
               marked in units of Arc seconds, arc minutes, or degrees
               TYPE = 1 astronomical labeling with Right ascension and
               declination.
       /PUTINFO - If set, then IMCONTOUR will add information about the image
               to the right of the contour plot.  Information includes image
               name, object, image center, image center, contour levels, and
               date plot was made
       XDELTA, YDELTA - Integer scalars giving spacing of labels for TYPE=1.
               Default is to label every major tick (XDELTA=1) but if
               crowding occurs, then the user might wish to label every other
               tick (XDELTA=2) or every third tick (XDELTA=3)
       XMID, YMID - Scalars giving the X,Y position from which offset distances
               will be measured when TYPE=0.   By default, offset distances
               are measured from the center of the image.
       Any keyword accepted by CONTOUR may also be passed through IMCONTOUR
       since IMCONTOUR uses the _EXTRA facility.     IMCONTOUR uses its own
       defaults for the XTITLE, YTITLE XMINOR, YMINOR, and SUBTITLE keywords
       but these may be overridden.

       (1) The contour plot will have the same dimensional ratio as the input
           image array
       (2) To contour a subimage, use HEXTRACT before calling IMCONTOUR
       (3) Use the /NODATA keyword to simply provide astronomical labeling
           of a previously displayed image.
       (4) The IMCONTOUR display currently does not indicate the image
           rotation in any way, but only specifies coordinates along the
           edges of the image

       Overlay the contour of an image, im2, with FITS header, h2, on top
       of the display of a different image, im1.   Use RA, Dec labeling, and
       seven equally spaced contour levels.    The use of a program like
       David Fanning's TVIMAGE  http://www.dfanning.com/programs/tvimage.pro
       is suggested to properly overlay plotting and image coordinates.  The
       /Keep_aspect_ratio keyword must be used.
       IDL> tvimage,im1,/keep_aspect, position = pos
       IDL> imcontour,im2,h2,nlevels=7,/Noerase,/TYPE,position = pos

       CHECK_FITS, EXTAST, GETROT, TICPOS, TICLABEL, TIC_ONE, TICS, XYAD
       CONS_RA(), CONS_DEC(), ADSTRING()

       Written   W. Landsman   STX                    May, 1989
       Fixed RA,Dec labeling  W. Landsman             November, 1991
       Fix plottting keywords  W.Landsman             July, 1992
       Recognize GSSS headers  W. Landsman            July, 1994
       Removed Channel keyword for V4.0 compatibility June, 1995
       Add _EXTRA CONTOUR plotting keywords  W. Landsman  August, 1995
       Add XDELTA, YDELTA keywords  W. Landsman   November, 1995
       Use SYSTIME() instead of !STIME                August, 1997
       Remove obsolete !ERR system variable W. Landsman   May 2000
       Added XMID, YMID keywords to specify central position (default is still
          center of image)  W. Landsman               March 2002
       Recognize Galactic coordinates, fix Levels display when /PUTINFO set
           W. Landsman                May 2003
       Correct conversion from seconds of RA to arcmin is 4 not 15.
               M. Perrin                                       July 2003
       Fix integer truncation which appears with tiny images WL  July 2004

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