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Download VERY LARGE TELESCOPE NACO User Manual
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User’s Manual VLT-MAN-ESO-14200-2761 Table 5-5: NACO Overheads Acquisition Templates Overhead Comment 3 min 0.75 min 2 min 5-10 min Depends on the brightness of the source used for AO Strehl measurement 4 min Not charged to the user Imaging acquisition 0.5 min Polarimetric acquisition 1 min Spectroscopic acquisition 1-5 min Depends on target brightness Coronagraphic acquisition 2-3 min Depends on target brightness SDI+4 acquisition 10 min Accurate centring is mandatory LGSF acquisition 10 min On top of the classical ACQ time Observation templates Readout overhead per DIT (FowlerNsamp) 2 sec Readout overhead per DIT × NDIT 0.7 sec (Double_RdRstRd) Readout overhead per DIT (Uncorr) Negligible Telescope Offsets 9 sec 1 NAOS header 7 sec 2 Stop and Start AO 2 sec 3 Start and completion overheads for IRACE 9 sec 4 1+2+3+4 = typical offset 27 sec 2+4 = time between frames without offsets 16 sec Change in instrument configuration 1 min HWP in (or out) 30 sec HWP angle setup 15 sec Rotator offset (for polarimetry and SDI) 1-2 min Re-centring for 4QPM and SDI+4 2 min All observations using chopping 30% Add to the exposure time Night time spectroscopic flats 6 min per on/off pair Night time spectroscopic arcs 6 min Night time coronagraphic flats 6 min per on/off pair Description Telescope Preset Guide star acquisition Initial setup (NAOS+CONICA) AO acquisition 98
