NAME:
  wrastfc
 PURPOSE:
  Write an astrometry fit coefficient file.
 DESCRIPTION:

 CATEGORY:
  File I/O
 CALLING SEQUENCE:
 wrastfc,file,ffn,ftype,xc,yc,prot,renormfac,cra,cdec,photzp, $
            terms,coeffarr
 INPUTS:
  file     - Output file name to be written.

  Each of these inputs are vectors or arrays.  The length of the vectors or
    the number of rows is equal to the number of fit coefficient sets in
    the file.  For arrays, the dimensions are [nlines,10]
  ffn      - File name for this fit.
  ftype    - Type of fit (eta or xi)
  xc       - X center of array
  yc       - Y center of array
  prot     - Pre-rotation of raw coordinates (degrees)
  renormfac- Renormalization factor used for solution.
  cra      - Center right acension (radians)
  cdec     - Center declination (radians)
  photzp   - Photometric zero-point for this image.  If the value is
               99.0 the zero point has not been determined.  This will
               allow you to later compute a real magnitude from instrumental
               magnitudes on the frame.
  terms    - string vector of names of terms to use (see astterms.pro)
  coeffarr - Array of astrometric fit coefficients (see astterms.pro)

 OPTIONAL INPUT PARAMETERS:

 KEYWORD INPUT PARAMETERS:

 OUTPUTS:

 KEYWORD OUTPUT PARAMETERS:

 COMMON BLOCKS:

 SIDE EFFECTS:

 RESTRICTIONS:

 PROCEDURE:

 MODIFICATION HISTORY:
  2003/06/30, Written by Marc W. Buie, Lowell Observatory
  2009/08/04, MWB, added prot and renormfac variables thus changing the
                      calling sequence (sorry)
  2009/12/01, MWB, upgraded to version 1.3 output, calling sequence changed
                      again (dropped ncoeffs as an input).