The total (or chargeable) observing time per observing block (or 'group') is calculated by adding all science exposure times and the detector readout times between them, plus a set 50 seconds for telescope slew and acquisition (the final detector readout is done as the telescope slews). The change in Cassegrain Adapter setup for the different polarimetry exposures that make up an observation can happen whilst the detector is reading out. Use the HARPS3 Exposure Time Calculator for the total science exposure time. A group is an observation of one target. If more than one group is necessary, enter how many.