Index
tilt_meter [state=on|off, limit=?]
Specify how and if the azimuth tilt meters are to be used.
- Mandatory Arguments:
- (none)
- Optional Arguments:
-
SwitchState state
- If this argument is
on
, then the azimuth tilt
meter readouts will be used to correct the pointing. If it is
off
then they will be ignored. In the archive
the tracker.corflags register can be used to determine whether
this tilt correction was enabled.
AngleLimit limit
- If the magnitude of either tilt meter readout is greater than
this number, then the tilt correction won't be made and the
overflow condition will be recorded in the tracker.corflags
register.
Example 1:
The following example enables the use of the tilt meters in the
pointing model, and specifies that if either of the tilt meter
outputs is outside of the range -100..100 arcseconds, this will
be considered an error.
tilt_meter state=on, limit=0:1:40
Example 2:
The following example stops the tilt meter from being used in the
pointing model.
tilt_meter state=off
Context:
In addition to a fixed misalignment of the azimuth axis, the
azimuth axis also tilts by varying amounts as the ground beneath
the telescope shifts and as the load on the front of the azimuth
platform changes with elevation. The former fixed tilt is
corrected by a constant term in the pointing model, whereas the
varying tilt is computed from on-line measurements of tilt meters
located on the azimuth platform. This command enables or disables
the use of the tilt meters to correct for the variable tilt.
To prevent a broken tilt meter from sending the telescope all over
the sky, a readout limit is required.
Note that the tilt meter is disabled and has a limit of zero
degrees when the system starts. An example of a suitable limit
would be about 100 arcseconds. The appropriate limit could be set
in the reboot file
(see load_reboot_script).
Martin Shepherd (6-Jul-2000)