The data products were individual FITS frames, one for each exposure.They were assembled offline into 3-D FITS cubes. For our purposes, we trimmed the cubes in time to about one second of data around the observed event, corresponding to ≈ 2″ on the sky. The data cubes were converted to a photometric light curve using a digital mask extraction, with the mask adapted for each event to match the seeing and image motion and to reject at the same time as much as possible of the background flux (see e.g. Richichi et al., 2008).