The first-half: None.

The second-half: The guider missed the guide star, and after restoration, and then the telescope was pointed to a wrong field. We need to recheck the pointing before continue the sequence. This occured twice, and for each time the process took about 30 mins. Four exposures were taken in the wrong field. Since there is no much time left when the second time happened, we just pointed the telescope to a direction roughly matching our target (withi 2 arcmin). However, even if we come back to the sequence, the focus has also been off and there was no time to fix, so we have to stop the observation earier. In total, there were 0.5 hr lost during the middle of the run, and another 1 hr lost at the end of the night due to the failed guiding + lost the field + defocus.