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+.help mkcwwcs Jun05 images.imcoords
+.ih
+NAME
+mkcwwcs -- make or update a simple celestial/wavelength wcs
+.ih
+USAGE
+mkcwwcs wcsname
+.ih
+PARAMETERS
+.ls wcsname
+Image to be created or modified.  If a new (non-existent) image is specified
+then a data-less image (NDIM=0) is created.
+.le 
+.ls wcsref = ""
+Image whose WCS is first inherited and then updated.
+.le
+
+.ls equinox = INDEF
+Equinox of the coordinates specified in decimal years.  If INDEF then the
+current value is not modified.
+.le
+.ls ra = INDEF
+Right ascension in hours.  This may be typed in standard sexagesimal
+notation though it will be converted to decimal hours in EPARAM and
+to decimal degrees in the WCS as required by the standard.  If INDEF
+then the current value is not modified.
+.le
+.ls dec = INDEF
+Declination in degrees.  This may be typed in standard sexagesimal
+notation though it will be converted to decimal degrees in EPARAM.
+If INDEF then the current value is not modified.
+.le
+.ls scale = INDEF, pa = 0., lefthanded = yes
+Celestial pixel scale in arc seconds per pixel, the position angle in
+degrees, and the handedness of the axes.  These are all represented by
+the WCS rotation matrix.  If the scale is INDEF the current
+rotation matrix is unchanged and the position angle is ignored.  If the
+scale is not INDEF then orthogonal axes are defined with the same scale on
+both axes.  The handedness of the axes are specified by the
+\fIlefthanded\fR parameter.  The position angle is measured from north
+increasing with the image lines (up in a standard display) and rotated
+towards east.  Note that if the axes are lefthanded the angle is
+counterclockwise and if not it is clockwise.
+.le
+.ls projection = "tan" (tan|sin|linear)
+WCS projection function for the celestial axes which may be
+"tan", "sin", or "linear".
+.le
+
+.ls wave = INDEF
+Reference wavelength in arbitrary units.  If INDEF then the current
+value is not modified.
+.le
+.ls wscale = INDEF
+Wavelength scale in arbitrary units per pixel.  If INDEF then the current
+value is not modified.
+.le
+
+.ls rapix = INDEF, decpix = INDEF, wpix = INDEF
+The reference pixel for the right ascension (first image axis), for
+the declination (second image axes), and for the wavelength
+(third axis).  The reference pixel may be fractional
+and lie outside the size of the image as allowed by the standard.
+.le
+.ih
+DESCRIPTION
+MKCWWCS creates or modifies a celestial (RA/DEC) plus wavelength
+three-dimensional WCS in an image header.  If a
+new image is specified the WCS is created in a data-less image header.  A
+data-less WCS may be used in various tasks as a template.  If a reference
+WCS is specified it is copied in whole and then desired elements of the WCS
+are modified.  If a new WCS is created without a reference the initial values
+are for the pixel coordinates.
+
+The elements of the WCS which may be set are the coordinate equinox,
+the right ascension and declination, the pixel scale, the axes orientation,
+the reference wavelength, the wavelength scale (i.e. dispersion),
+and the reference pixel in the image which corresponds to the specified
+right ascension and declination.  If values are specified the WCS elements
+are left unchanged.
+
+The WCS is simple and not completely general because it defines the first
+coordinate axis to be right ascension, the second to be declination, and
+the third to be wavelength.  The axes are orthogonal and the celestial axes
+have a uniform pixel scale (apart from the effects of the projection
+function).
+.ih
+EXAMPLES
+1. Create a data-less header by specifying a new wcs name.
+
+.nf
+    cl> mkcwwcs new ra=1:20:23.1 dec=-12:11:13 wave=5500. \
+    >>> scale=0.25 wscale=1.23
+.fi
+
+The reference pixel will be (0,0,0).  To apply it later to an actual
+image (say with WCSCOPY) would require assigning the reference pixel.
+Note the use of sexagesimal notation.
+
+2. Modify the WCS of an existing image by changing the reference value
+and pixel.
+
+.nf
+    cl> mkcwwcs old ra=1:20:23.1 dec=-12:11:13 wave=5500. \
+    >>> rapix=1234 decpix=345 wpix=1024
+.fi
+.ih
+SEE ALSO
+wcsedit,wcscopy,mkcwcs
+.endhelp