VLT-MAN-ESO-14650-4942
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24.06.2015
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ESO, Karl-Schwarzschild-Str. 2, 85748 Garching bei München, Germany
3.4.4 Nodding along the slit (SLIT only)
This corresponds to the standard way of observing in the near-IR primarily aimed at a double
pass sky subtraction. The template XSHOOTER_slt_obs_AutoNodOnSlit automatically
nods the telescope between two positions (A and B) along the slit. The user defines a Nod
Throw and optionally a small jitter box (in the slit direction). The Nod Throw is defined as the
distance between the two nodding position i.e. the center of the two jitter boxes inside the slit
(see Figure 17). Ditto for the jittering box, the jitter value corresponds to the size of the box.
One cycle is a pair of AB or BA observations. Cycles are repeated in ABBA sequences. For
each arm, the user chooses the number of exposures at each position and the exposure time
(both identical for all A and B positions). Exposures are asynchronous. Note that nodding is
not offered in IFU mode because the field of view (4”x1.8”) is too small to nod within the IFU.
Also note that it is not possible to move the target in one arm independently from the other
arms.
Figure 17: conventions used for nodding of 4” along slit observations. The sequence illustrated here
corresponds to 4 cycles (8 exposures, ABBAABBA) with a jitter box of 1”.
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