def get_mask_bool(mask, threshold=1e-3):
    """
    Return a boolean version of the input mask.

    Parameters
    ----------
    mask : enmap
        Input sky mask.
    threshold : float, optional
        Consider values below this number as unobserved (False).

    Returns
    -------
    mask_bool : bool enmap
        Boolean version of input mask.
    """
    # Makes a copy even if mask is already boolean, which is good.
    mask_bool = mask.astype(bool)
    if mask.dtype != bool:
        mask_bool[mask < threshold] = False
    return mask_bool