Make an empty sky region at location of skydir
    skydir : skymaps.SkyDir object
    size   : size of region (deg.)
    kwargs : arguments passed to create_header

def create_header_data(coord, radius=10., **kwargs):
    """ Make an empty sky region at location of skydir
    skydir : skymaps.SkyDir object
    size   : size of region (deg.)
    kwargs : arguments passed to create_header
    """
    header = create_header(coord, radius=radius, **kwargs)
    data = np.zeros( (header['NAXIS1'],header['NAXIS2']) )
    return header, data