Set the integration per frame to the value showed in the figures 3.3 to 3.5 and check for saturation effects (Linearity range is 21800 ADU). Use the ON/OFF mirror for switching between object, reference star and sky. If the reference star is not within the object frame, record only few frames (about 10) per ON/OFF setting, because the shape of the point spread function can vary rapidly. Remember, that at least one frame is lost when moving the ON/OFF mirror. To avoid memory effects, increase number of wait frames when moving the ON/OFF mirror, or throw away the bad frames afterwards (recommended).