def bad_acq_stars(stars):
    """
    Return mask of 'bad' stars, by evaluating AGASC star parameters.

    :param stars: astropy table-compatible set of agasc records of stars. Required fields
          are ['CLASS', 'ASPQ1', 'ASPQ2', 'ASPQ3', 'VAR', 'POS_ERR']
    :returns: boolean mask true for 'bad' stars
    """
    return ((stars['CLASS'] != 0) |
            (stars['MAG_ACA_ERR'] > 100) |
            (stars['POS_ERR'] > 3000) |
            (stars['ASPQ1'] > 0) |
            (stars['ASPQ2'] > 0) |
            (stars['ASPQ3'] > 999) |
            (stars['VAR'] > -9999))