Changes

The purpose of this step is to figure out where on the acquisition image you need to place your star, in order for it to land close to the ideal spot on the slit. Very bright stars can be seen reflected on the slit jaws, and can be placed on the slit directly, but this is not the case for fainter stars, which need the superior reflectivity of the guide mirror in order to be seen on the acquisition camera. This position should be approximately stable throughout your run, but it is worth checking every couple of days that you can fine-tune the red box on target location using the acquisition camera screen still corresponds to the appropriate position on the slit. This is much easier now that the instrument has a rear-of-slit camera!.

* # Move the guide mirror into the beam, either by setting the ''Acquisition'' state in the ''Lamp/Mirror Settings'' pane of the SpUpNIC control GUI (if it says Guide Mirror ''Science'', click ''Change''), or by clicking on the guide mirror in the instrument schematic. * # Acquire a bright star (e.g. ~4th mag from the Bright Stars chapter of the Sutherland Almanac, available in the warm room), roughly centre it in the acquisition camera field and continue exposing. * # Move the guide mirror out of the beam (i.e. centre the mirror so that light can go down the central hole). * # Move the rear-of-slit mirror into the beam (''Lamp/Mirror Settings'' pane, RoS mirror change from ''Out of beam'' to ''In beam''). * # Turn on the slit illumination (in the ''Instrument Setup'' pane, ''Change'' to turn on the lamp). Tune the exposure time/LUT sliders on the TCS until you can clearly see the slit running horizontally across the acquisition image, approximately halfway up. * # Using the hand paddle, move the telescope to place the star on the slit, approximately one quarter of the image width away from the right-hand edge. * # Turn off slit illumination. * # Click on the icon [[File:Potcamicon.jpg|40px]] for the rear of slit camera (on the left-hand side of Monitor 1). * # An image window for the rear-of-slit camera will pop up. This looks up at the slit from below, 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. [[File:slit_view.png|thumbnail]]* # 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 the Quick-Look GUI, on Monitor 2. You are aiming for the spectrum to fall on approximately the central row of pixels within the image area (note that this is a roughly central band that only covers about half the vertical extent of the CCD). 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, go back to the TCS and 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.