pro nm_xy2radec, x, y, outra, outdec, crpix1, crpix2, crval1, crval2, cd11, $
                 cd12, cd21, cd22
 
  xi  = cd11 * (x - crpix1) + cd12 * (y - crpix2)
  eta = cd21 * (x - crpix1) + cd22 * (y - crpix2)
 
  xi   = xi  * !pi / 180.0
  eta  = eta * !pi / 180.0
 
  ra0  = crval1 * !pi / 180.0
  dec0 = crval2 * !pi / 180.0
 
  ra  = atan(xi, cos(dec0)-eta*sin(dec0)) + ra0
  dec = cos(dec0)-eta*sin(dec0)
  dec = (dec)*(dec) + xi*xi
  dec = atan(eta*cos(dec0)+sin(dec0), sqrt(dec))
 
  ra  = ra  * 180.0 / !pi
  dec = dec * 180.0 / !pi
  ra = ra mod 360.0
  if (ra lt 0.0) then ra = ra + 360.0
 
  outra = ra
  outdec = dec

end