def stringify_dict(dic, ignore_types=(str, int, float)):
    """
    Turns a dict entries into strings for addition to FITS headers
    """
    from copy import deepcopy
    dic_new = deepcopy(dic)
    for key in dic_new:
        if not isinstance(dic_new[key], ignore_types):
            dic_new[key] = str(dic_new[key])
    return dic_new
