def set_orb_ticks(axis):
    """
    Set major ticks to multiples of 1, minor ticks to 1/4.
    """
    from matplotlib.ticker import MultipleLocator
    xMticks = MultipleLocator(2.0)
    xmticks = MultipleLocator(0.5)
    yMticks = MultipleLocator(2.0)
    ymticks = MultipleLocator(0.5)
    axis.xaxis.set_major_locator(xMticks)
    axis.xaxis.set_minor_locator(xmticks)
    axis.yaxis.set_major_locator(yMticks)
    axis.yaxis.set_minor_locator(ymticks)
    axis.grid(True)
