HEADER

        HEADER [Image_Name] /EXTREMA

    Compute the extrema of the current or specified image,  and  update  the
    header accordingly.

        HEADER /UPDATE

    Update the header of the current image, for example after  modifications
    to the G_* header variables have been made. The header variables are
    G_NDIM         Number of dimensions
    G_DIM[4]       Image dimensions
    G_CONVERT[3,4] Conversion formula (Ref, Val, Inc for each axis)
    G_BLANK[2]     Blanking and tolerance
    G_MAX          Maximum value
    G_MIN          Minimum value
    G_EXTREMA      Zero (0) if no extrema defined
    G_WHERE[2,4]   Pixel of maximum and minimum
    G_UNITi        Units of axis i
    G_UNIT         Units of map
    G_COORD        System coordinates
    G_SOURCE       Source name
    G_EPOCH        Epoch of coordinates
    G_RA           Right Ascension (of Object)
    G_DEC          Declination (of Object)
    G_LII          Galactic longitude (of Object)
    G_BII          Galactic latitude (of Object)
    G_PTYP          Projection Type (0:none,1:Gnomonic,2:Orthographic,
                    3:Azimuthal,4:Stereographic,5:Lambert,6:Aitoff,7:Radio).
                    Warning: these codes are subject to change without notice.
    G_XAXI         The first axis of projection (1,2,3 or 4)
    G_YAXI         The second axis of projection (1,2,3 or 4)
    G_A0           Position of projection center for axis G_XAXI (R.A. or LII)
    G_D0           Position of projection center for axis G_YAXI (DEC. or BII)
    G_ANGLE        Angle of projection (East of North)
    G_LINE         Line name
    G_FREQRES      Frequency resolution
    G_RESTFRE      Signal rest frequency
    G_FREQOFF      Image rest frequency
    G_VELRES       Velocity resolution
    G_VELOFF       Velocity of reference channel
    G_PA           Position angle of beam
    G_MINOR        Minor axis size of beam
    G_MAJOR        Major axis size of beam
    G_BEAM         Size of RESOLUTION section (0 or 3)

        HEADER [Image_Name] [/OUTPUT FIle_Name]

    Give the Header of the current or specified Image, on the screen  or  in
    the  specified output file.  Provided you have write access to the image
    and nobody else is already using it, the header may be  editted  if  the
    terminal  is  a  VT100 compatible. The keys of the VT100 keypad have the
    same meaning as in EDT:
               +--------+--------+--------+--------+
               |  enter |        |        |  Del L |
               |  edit  |        |        |        |
               +--------+--------+--------+--------+
               |  print |        |        |  Del W |
               |  header|        |        |        |
               +--------+--------+--------+--------+
               | Advance| Backup |        |  Del C |
               |        |        |        |        |
               +--------+--------+--------+--------+
               |  Word  |   Eol  |  Char  |        |
               |        |        |        |  Enter |
               +--------+--------+--------+        |
               |       Line      |        |(Update)|
               |                 |        |        |
               +-----------------+--------+--------+
     To edit a field, press the GOLD (PF1) key.
     To compute MAXIMA and MINIMA of current image, strike ENTER key.
     Strike <^Z> to exit.
     The header will be automatically updated if any modification  has  been
    made.