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On the other hand, the command OFFSETS
can be used to specify additional position offsets in other systems.
These globally defined offsets stay fixed during a complete scan.
They are only needed in special cases, e.g., the Nasmyth offsets
or for ONOFF with wobbler switching, see below.
At this time (),
the command OFFSETS supports offsets in the following 3 systems:
- projection
- Offsets in
the ``radio'' projection (see above).
- trueHorizon
- ``true angle horizon'' offsets in Azimuth and Elevation:
where
and
are the Azimuth and Elevation of the telescope;
and
are the Azimuth and Elevation of the source,
calculated from
and
(and the time and other parameters).
- Nasmyth
- offsets in the Nasmyth (receiver cabin) system.
The purpose of Nasmyth offsets is exclusively to
re-position the telescope so that an off-center
element of a multibeam receiver looks at the
position where otherwise the center pixel would look.
E. g.,
OFFSETS -33 44 /SYSTEM Nasmyth
adds offsets -33 and 44 in the Nasmyth
system (for all observing modes!)
Next: Example 1
Up: Coordinate Systems, Map Projections,
Previous: Map Projections and Offsets.
Contents
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Gildas manager
2023-06-01