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LUCIFER User Manual
Issue 1.3
29
2. a *.epsf file containing a picture of the mask for direct view (does not show the mask ID),
3. two Gerber files, *.grb, and * v2.grb cointaining the information for mask cutting. The *.grb
file is used for the mask cutting machine available in Munich, the * v2.grb file can be read by
the LBT mask cutting machine.
6.2
Offset and position angle definition
On the LUCIFER images, for a position angle null, North is towards the top of the image, while East
is towards the right, unlike the typical orientation of astronomical images. The position angle you
give is however defined the classical astronomical way = from North to East and given in
degrees.
All offsets are defined in arcseconds. The telescope can be offsetted either in RA/DEC, the
coordinate system is then defined as RADEC), or along the lines/columns of the detector, the coordinate
system is then DETXY. The latter is very useful for e.g. long slit spectroscopy. One also has to define
the type of offset:
- cumulative, the offset type is then relative and one moves relative to the last position, or
- absolute, where all offsets refer to the original position. When offsetting the RADEC, one basically
tells the telescope where to go; the object on the detector will move in the opposite direction. Offsets
in DETXY defines where the object will move on the detector.
The active optics duty cycle is typically of 45 seconds, it is therefore recommended to spend at least
one minute per position after/before offsetting.
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Figure 12: Illustration of the star motion defining a relative offset pattern in RADEC (left) or DETXY
(right). For offsets in DETXY coordinates, the position angle does not make any difference, the object
will always move the same way on the detector. Offset list: (0,0) - (60,60) - (-120,0) - (0,-120) - (120,0).
6.3
Overhead Calculations
Each read is associated with a given readout time, it is 2 seconds in DCR mode and 10 sec in MER
mode. Please note that an integration of 1 minute defined as 2 seconds × 30 NDIT will have a 50%
duty cycle, i.e. it will use 2 minutes of time to complete this 1 minute of on-source integration.