Download EFOSC2 Manual 3.1

EFOSC2 USER’S MANUAL - 3.1
LSO-MAN-ESO-36100-0004
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Figure 10: Default EFOSC2 CCD orientation.
The full specifications of CCD#40 are given in Table 6. The array has one serial register and two
output ports; one port at each end of the register. This thinned CCD achieves its high quantum
efficiency in the blue and UV through UV flooding of the backside. The quantum efficiency curve is
plotted in Fig. 12.
Note that even though the CCD has 2048 × 2048 pixels, the image size is 2060 × 2060. In fact,
during the read out process 12 rows and 12 columns are added (see Fig. 11). We remark that these
additional pixels cannot be used as a real over-scan, since the region is too small and contaminated
by the adjacent area during the charge transfer process. The observer should therefore take bias
images at the beginning and/or end of the night.
The CCD is driven by the new ESO–FIERA controller. FIERA has two amplifiers (L and R) and
offers 3 different read out speeds. Three modes are currently offered (slow, normal and fast). As it is
shown in Table 6, there is not a big improvement in terms of R.O.N. using the slow mode. For this
reason the normal mode should be used for the scientific images. The bias level for the three modes
is ∼ 220 ADUs.
The CCD system (CCD+FIERA controller) shows a linearity better than 0.4% over the full range
of the 16 bit analog to digital converter (ADC). The system linearity has been explored in a range
of 2000 e− up to 83000 e− . The electronics have been tuned so that the ADC will saturate before
non-linearity is reached. Hence the full range (∼200-65535) is usable for scientific purposes. Even in
cases of strong saturation the residual effect is very small and it is completely removed by taking a
few bias frames.
When a short read-out time is required (for instance during the acquisition phase) the fast mode can
be used. Using 2 × 2 binning allows the CCD to be read in about 9 seconds, at an equivalent data
transfer rate of 113 kpx s−1 . The user must be aware that this mode makes use of both amplifiers
(L and R) and hence produces images with two different bias levels. During the target acquisition
this is not a problem. However, the user can select the normal read-out mode also for the target
acquisition images, in such a way that he/she can use them also for scientific purposes. Alternatively,
the user can take flats, biases and standards in the fast mode for calibrating the data.
The web site:
http://www.eso.org/sci/facilities/lasilla/instruments/efosc/inst/Ccd40.html
gives more information about the CCD#40. Additionally, the user can have a look at the weekly