def plot_scatter(ax, photon_events, pointsize=1, **kwargs):
    """Make a scatterplot
    This is effcient when there are a low RIXS intensity

    Parameters
    ----------
    ax : matplotlib axes object
        axes for plotting on
    photon_events : array
        two column x, y, Iph photon locations and intensities
    pointsize : float
        multiply all point sizes by a fixed factor
    **kwargs : dictionary
        passed onto matplotlib.pyplot.scatter.
    Returns
    ----------
    image_artist : matplotlib artist object
        artist from image scatter plot
    """
    ax.cla()
    ax.set_facecolor('black')
    defaults = {'c': 'white', 'edgecolors': 'white', 'alpha': 0.5,
                'pointsize': pointsize}

    kwargs.update({key: val for key, val in defaults.items()
                   if key not in kwargs})

    pointsize = kwargs.pop('pointsize')
    image_artist = ax.scatter(photon_events[:, 0], photon_events[:, 1],
                              s=photon_events[:, 2]*pointsize, **kwargs)
    return image_artist