def start_log(level=logging.DEBUG, filename=None):
    """start the logger for the run

    Parameters
    ----------
    level : int, optional
        logging.DEBUG, logging.INFO etc. for the log level (between 0-50).
    filename : str, optional
      name of the filename to save the log to or
      None (default) to use deblur.log.TIMESTAMP
    """
    if filename is None:
        tstr = time.ctime()
        tstr = tstr.replace(' ', '.')
        tstr = tstr.replace(':', '.')
        filename = 'deblur.log.%s' % tstr
    logging.basicConfig(filename=filename, level=level,
                        format='%(levelname)s(%(thread)d)'
                        '%(asctime)s:%(message)s')
    logger = logging.getLogger(__name__)
    logger.info('*************************')
    logger.info('deblurring started')