Specify the encoder angles at zero azimuth, elevation and deck angle.

Arguments:

PointingOffset az

The azimuth encoder angle that corresponds to zero azimuth, measured in the direction of increasing azimuth.

PointingOffset el

The elevation encoder angle that corresponds to zero elevation, measured in the direction of increasing elevation.

PointingOffset dk

The deck encoder angle that corresponds to the chosen zero point of the deck axis, measured in the direction of increasing deck angle.

Optional Arguments:

Camera number

The number of the associated optical pointing camera. If this is omitted, the pointing model of the currently selected camera is configured.

Example:

The following example tells the control system that when the telescope is pointing north, the azimuth encoder actually reads 10.5 degrees. Also that when the telescope is pointing at zero elevation that the elevation encoder reports an elevation of -4.3 degrees. And finally that when the deck encoder reads -50.0 degrees the deck angle should be considered to be zero.

 encoder_zero_points 10.5, -4.3, -50.0

Context:

The angles at which azimuth and elevation encoders report zero counts do not correspond to the zeroes of topocentric azimuth and elevation. This is both because manually positioning the encoders to arcsecond accuracy is virtually impossible, and because the zero points will gradually change as the telescope base sinks and other parts of the telescope relax. Instead these zero points are deduced by offline software while fitting the pointing model of the telescope, ready to be installed with the encoder_zero_points command.

Note that after a reboot the control system will refuse to track a source or slew the telescope until this command has been called, so this should be done from the $CBI_DIR/conf/rtc.init boot script.