From the point of view of the observer, the execution of a single OB, after image analysis, has the following global overheads:
To these, the following "fixed" overheads should be added:
In total, there are therefore 120s for the initial preset + 240s for IA + 45s at the start of the OB + 60s for each image.
From these numbers it is clear that the longer the single exposure time, the smaller the impact of overheads, although the single exp. time depends, of course, on specific scientific requirements. If real-time image analysis is implemented, it will be possibile to reduce or eliminate the IA cycles before OB execution, thus remarkably reducing global overheads. Real-time IA is currently in a testing phase.
The first image analysis (4-5 cycles) is done at the beginning of the night during nautical twilight and does not affect scientific time. When possible, also photometric standards are observed during twilight, both evening and morning.