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NOTE: The following is still based on discussion from the old manual. New data has been obtained, but has not yet been fully reduced into a format for inclusion into the present document. Performance, however, is comparable to that when Hydra was in use on the Mayall telescope.
Peak system throughput (ratio of detected photons to number incident on the primary mirror) can be as high as 5% in the red under good seeing conditions (FWHM seeing of 1.0 arc-seconds) on a fiber that is placed at the center of the field.
Figure 9 shows the number of photons per second per Å detected for the standard star Feige 66 (m3500=9.8, m4500=10.1, m5000=10.3) observed with the blue cable, firstname.lastname@example.org grating, T2KB CCD detector, and the Simmons Camera.
Figure 9: Flux counts with the blue fiber cable. UPDATED FIGURES NOT YET AVAILABLE
The dropoff on the blue end is dominated by atmospheric extinction and the rapidly declining quantum efficiency of the CCD detector. The grating blaze function and color of the star are the predominant terms defining the slope on the red end of the spectrum.
Estimates of exposure time can be extrapolated from Figure 9 by scaling the grating dispersion and blaze efficiencies, CCD QE, fiber throughput, filter transmission, and object magnitudes.