def getHeader(self,exten=None):
        """ Return just the specified header extension fileutil
            is used instead of fits to account for non-FITS
            input images. openImage returns a fits object.
        """
        _image=fileutil.openImage(self._filename, clobber=False, memmap=False)
        _header=fileutil.getExtn(_image,extn=exten).header
        _image.close()
        del _image
        return _header