X-shooter
User Manual
Doc:
Issue
Date
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VLT-MAN-ESO-12000-0115
1
01.03.2009
25 of 60
ESO, Karl-Schwarzschild-Str. 2, 85748 Garching bei München, Germany
the expected limiting AB magnitudes at blaze in 1 hour for a S/N of 10 per spectral bin are
given in Figure 9. Please keep in mind that for the NIR arm, theses are first estimates based
on engineering data only: they will be measured at the telescope during forthcoming
commissioning runs.
.
Figure 9: Limiting AB magnitude of X-shooter per spectral bin (using 2 pix binning in the spectral
direction) at S/N=10 in a 1 hour exposure. Other parameters: air mass 1.2, 0.8” seeing, 1” slit for UVB,
0.9” slit for VIS and NIR. The first version of the ESO ETC was used to compute these values. The
model uses overall efficiencies measured during commissioning for UVB and VIS. For the NIR arm
however, it uses as-built values for optics and detector efficiency/noise. Note that these performance
estimates assume no degradation of the SNR in the extraction process or in the sky subtraction. The
decrease in efficiency to the blue side of the UVB range is due to the atmospheric absorption, at the
red side of the VIS band it is due to the decrease in efficiency of the CCD, while on the long-
wavelength side of the NIR range it is due to the rise of the thermal background.
500
1000
1500
2000
Wavelength [nm]
22
21
20
19
18
Limiting AB magnitude (1h, SNR=10)
