* An image window for the rear-of-slit camera will pop up. This looks up at the slit from behind, to enable you to check that your star is centred on the slit. Move the telescope such that the star falls on the centre of the slit image in both x and y.
* Move the rear of slit mirror out of the beam and take a test spectrum (e.g. 20 seconds) of the bright star (in the ''Exposure/CCD info'' pane, select ''Exposure type'' = SCIENCE from the drop-down menu, enter ''20'' in ''Exposure time'' and click ''Expose'').
* The resulting image will be displayed on Monitor 2. You are aiming for the spectrum to fall on approximately the central row of pixels. If the spectrum is too high or low, move the telescope slightly in RA(the RA- button moves the spectrum downwards in the image), iterate until the star is well positioned.
* Once you are happy with the position of the spectrum on the image, on the TCS, add a red marker over the position of the star on the slit (TCS ''Pointer'' pane: ''Markers'', ''Add a red marker'').
* Finally, move the guide mirror into the beam, and add a second red marker at the position of the star. This marker will be used to approximately position stars on the slit that are too faint to be seen reflected off the slit jaws.