Changes
/* Setting up the grating */
====Setting up the grating====
* '''Observers must not handle the gratings - only trained and authorised technicians may do so.''' Before your run you will receive a google form to submit to request your required grating be installed for you. If you need a grating change during your run, you must contact the standby technician.
* SpUpNIC suffered severe grating instability problems that were incrementally reduced through various interventions, the last of which was the introduction (in early November 2016) of a pneumatically-actuated lock to clamp the grating mechanism at the user-defined angle. The lock is under software control and can thus be de-activated by the user in order to adjust the grating. We are delighted to report that the lock has eliminated the last of the play within the grating mechanism! Flexure remains inevitable for a Cassegrain spectrgraph as it swings about the sky on the back of the telescope. Therefore we still recommend that users bracket their target observations with arcs (taken immediately before and after the object exposures) so as to calibrate out any remaining shifts due to flexure.
