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VIMOS User Manual
VLT-MAN-ESO-14610-3509
object of interest is of limited size in LR mode, and if only the central 1/4 × 1/4 of the field of view is
needed, it is possible with the IFU Shutter option to mask the outer part of the IFU (always masked
in MR and HR modes). This allows to avoid second order overlap due to sky and / or background
objects between the 4 adjacent slits along the dispersion direction. True means that the shutter is in
place and masks the external part of the IFU, False (the default value) means that the mask is not in
place and the full IFU field of view is available. To produce a valid OB, the mask shutter option
should be the same in every template of the OB. This parameter is ignored when MR or HR grisms
are used.
• Return to Origin? (T/F). This parameter defines whether or not, after a dithered set of observations, the telescope will return to the reference position. This parameter is in general to be left in
the default value (T) in service mode. If another value is desired in service mode a waiver should be
requested.
• Number of Telescope Offsets?. This parameter defines the number of telescope offsets during the template. The number of exposures taken at each telescope position is determined by the
next parameter (Number of exposures per telescope offset ?). The pattern of offset
is defined in the List of offsets (arcsec) CORRECT LABEL and List of offsets
(arcsec) CORRECT LABEL parameters.
• Number of exposures per telescope offset?. This parameter defines how many exposures are taken for each offset position.
• List of offsets (arcsec) List of offsets between exposures. Offsets are defined relative to
the previous position. The offsets are defined in RA/DEC. If the first image is to be taken at the preset
coordinates, the first set of offsets should be 0,0. If there are less offset values than the defined number
of offset positions, the template will return at the beginning of the list of offsets and apply them again.
For example, if 5 telescope offsets are defined (Number of Telescope Offsets?) together
with the following series of offsets ( apparent movement of the target on the detector in RA/DEC):
RA
DEC
0
0
-10
5
-5
10
the offsets applied to the telescope will be (see also Sect. 4.6.1):
RA
DEC
0
0
10
-5
5
-10
0
0
10
-5
• Observation Category. SCIENCE is for a regular science IFU program. Never choose TECHNICAL.