#### Global Offsets.

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!)