Figure 12.1: Total throughput.
When observations are made through sufficiently large apertures, and proper account is taken for atmospheric absorption and telescope mirror reflectance, the photon throughput of the telescope, spectrograph, and TI CCD is as high as one could hope. Figure 12.1 shows the total throughput for the 600 g/mm (3568)Å and 300 g/mm (6690)Å gratings, peaking around 13%.