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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.