Changes
/* Setting up the grating */
====Setting up the grating====
* '''N.B.''' We have now installed a physical brake on the grating to address the instability problem mentioned below. This means that you can not change the grating angle when the brake is applied, and we have disabled the ability to change the grating angle in software. This can be re-enabled, but only when the brake is not applied. A technician is therefore required to disable the brake and change the grating angle.
* '''Warning:''' During your start-off you will have been told about the grating instability problem. We applied a mechanical fix when the instrument is off the telescope in early April. This improved the situation, but did not completely resolve the issue - so until such time as we have completely fixed the problem, we urge users to bracket all target observations with arcs (to be taken immediately before and after the object exposures) to minimise the impact of the declination-dependent movement of the grating.
