Before the Spectrograph is used a choice should be made of optics, grating and slit. Although either set of optics can be used throughout the wavelength range 350 to 1000,nm, there is an efficiency penalty. The performance data should be consulted, but as a general guide, red optics should be used for wavelengths above 500,nm.
The choice of slit will depend on the seeing but it is anticipated 1that the 1,arcsec slit will be the normal choice.
The choice of grating will be governed by the observations and the dispersion and wavelength data should be consulted.
The ``mounting'' of the optics should only be attempted by someone familiar with the spectrograph.
New users can quickly learn the necessary procedures which, with everything to hand, takes about 20 minutes for a complete optics changeover. Many of the mounting screws mate with threads tapped into aluminium and care should be taken not to overstress the threads, i.e., a light hand is required. The grating should not be removed without having a protective cover in place. It is wise to cover the grating during most operations within the casing with the lid removed.
OBSOLETE:In such operations the EHT to the exposure 'C@: met stitched off and as an additional precaution the me or e c is now described