The keywords covered by [stage]abort are:
So, for example, to halt the Echelle grating, the command would be:
modify -s nsmotor echellestp=1
The keywords covered by [stage]init are:
So, for example, to init (i.e. calibrate) the Echelle grating, the command would be:
modify -s nsmotor echellecal=1
In normal operations, the image rotator tracks in different directions depending on the location of the object in the sky:
The Rotator GUI software is smart enough to be able to find the correct slit position on the sky and have the rotator track accordingly. Once you input the Rotator Mode (i.e. position angle) and the Slit PA destination value, you can see where the physical limits are for the rotator as it slews to the tracking position (left panel on the GUI). If the positon is close to a limit (i.e. 90 or 270 physical) and tracking towards it (shown by the yellow directional arrows), you may want to consider the 180-degree complement of your desired PA to ensure you will have a safe amount of time to observe before reaching the rotator limit.