X-shooter
User Manual
Doc:
Issue
Date
Page
VLT-MAN-ESO-12000-0115
1
01.03.2009
26 of 60
ESO, Karl-Schwarzschild-Str. 2, 85748 Garching bei München, Germany
2.4
Instrument features and problems to be aware of
2.4.1 UVB and VIS detectors sequential readout
UVB and VIS detectors share the same FIERA controller. While both arms can expose
simultaneously, readout is done sequentially. In practice, this means that if an exposure
finishes in one of the arms while the other one is being read out, it has to wait until the first
one is fully readout and transferred to disk until readout can start.
2.4.2 Remnance
TBD
2.4.3 Instrument stability
Backbone flexures
The active flexure compensation allows to maintain the three slits aligned with respect to the
reference A&G pinhole to within ~0.02” in both at any rotation angle for ZD<60˚. Without the
flexure compensation running (e.g. in case of failure of the calibration lamp during the night),
this alignment is kept within ~0.1” (measured for UVB and VIS only for now).
Spectrograph flexures
From 0˚ to 60˚ zenithal distance for any rotator angle, the spectra format in all three arms
stays within ~1.2 pixels from the zenith position.
