Index
rotcor [state=on|off,
limit=?, encoder_zero=?, shaft_zero=?]
Specify how and if the elevation rotation meters should be used.
- Mandatory Arguments:
- (none)
- Optional Arguments:
SwitchState state
- If this argument is
on
, then the
readouts of the rotation meters on the elevation shaft and
encoder body will be used to correct the pointing for the
anomalous twisting of these members. If it is
off
then they will be ignored. In the
archive the tracker.corflags register can be used to
determine whether this correction was enabled.
AngleLimit limit
- If the magnitude of either rotation meter readout is greater than
this number, then the correction won't be made and the
overflow condition will be recorded in the tracker.corflags
register.
Angle encoder_zero
- This can be used to specify a zero offset for the
encoder-body rotation correction.
Angle shaft_zero
- This can be used to specify a zero offset for the
elevation-shaft rotation correction.
Example 1:
The following example enables the use of the rotation meters in
the pointing model, and specifies that if the sum of the rotation
meter outputs is outside of the range -100..100 arcseconds, this
will be considered an error.
rotcor state=on, limit=0:1:40
Example 2:
The following example stops the rotation meters from being used
in the pointing model, without changing any previously
established correction limit.
rotcor state=off
Example 3:
The following example specifies zero offsets for both of the
rotational corrections, 5 arcseconds for the encoder-body
rotation correction, and 1 and half arcminutes for the elevation
shaft correction.
rotcor encoder_zero=0:0:5, shaft_zero=0:1:30
Context:
As the elevation of the telescope changes, small distortions in
the normally unmoving elevation shaft and the encoder mount
result in an apparent rotation of the encoder shaft, thus
changing the elevation readout from what it should be. Rotation
meters measuring these twists can be used to correct for this
effect.
To prevent a broken rotation meter from sending the telescope all
over the sky, a readout limit is required.
The arbitrary zero points of the rotation meters slowly vary,
so this command provides a way to specify zero offsets.
Also see the zero_rotcor command
for an alternate way to set the zero offsets.
Note that the rotcor is disabled and has a limit of zero degrees
and no zero offsets 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)