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 stable throughout your run, but it is worth checking every couple of days that the red box on 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!