Starlight emerges in an f36 beam from the 3-meter's hollow polar axle (or from the CAT portal), coming to a focus on the slit jaws, located in the slit room.

After passing through the slit, the light enters the camera room, passing through a filter wheel and an electronic shutter. Traversing the camera room, the beam is reflected from the Hamilton's off-axis collimating mirror to the echelle grating. Next come two large cross-dipersing prisms which separate the spectral orders perpendicular to the dispersion. Finally an f1.7 Schmidt camera focuses the spectra onto the CCD detector. The CCD is housed in a liquid nitrogen dewar, mounted on a fine-motion stage for focusing and positioning.

(Apologies for the nearly illegible captions in the above figure. I'm working on a better pstogif solution.)