LUCIFER User Manual Issue 1.3 31 Table 10: Overview of all overheads times Action type Time (sec) Pointing correction 420 Pure preset Collimation of active optics 70 135 Offset time Track mode Guided mode + active optics on 4 18 Motion of mask (turnout to FPU) 45 Read out time DCR mode MER mode 2 10 Time to write a file 12 different occasions with LUCIFER, under clear weather conditions, using the N3.75 camera. Table 11 presents some typical results, where the limiting integration time has been rounded. Filter Sky flux (e− /sec) No Moon DIT lin (sec) BLIP (sec) z J H K Ks 47 290 1315 3250 1640 3900 600 140 50 110 6 < < < < H2 Br gam FeII P beta P gam 115 125 97 42 18 1600 1400 1800 4300 10000 2.5 2.3 3 7 16 minDIT minDIT minDIT minDIT 70% Moon illumination Sky flux DIT lin BLIP (e− /sec) (sec) (sec) 120 1400 2.5 2400 4300 75 40 < minDIT < minDIT Table 11: Measured (N3.75 camera) sky emissivity and corresponding integration time to have the sky background reaching the linearity limit (determined as two third of the full well) and to be background limited. The background-limited performance (BLIP) is defined as : t BLIP = 2×RN2 / Skyflux. It determines the minimum DIT needed to be background limited, defined here for imaging observations in DCR mode (minDIT ∼ 2sec) with the N3.75 camera. 6.5.1 Imaging During clear nights, photometric standard stars have been observed in imaging mode with the N3.75 camera and all available filters. Table 12 presents the derived zero points for all filters. Please note that the LUCIFER1 z & J broad band filters are wider than the corresponding atmopheric windows (as illustrated in Fig. 13). As a consequence the measured zero points in these bands are quite sensitive to the amount of water vapor in the atmosphere, resulting in flux variations of 3% in z and 6% in J when the atmospheric water vapor doubles.