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Faint Object Red Spectrograph (FORS)

The equivalent figure-of-merit for FORS is AB6600=17.5, which will give 1 electron/s/Å. In dark time, with 2" seeing and a 1.5" slit, a star with R = 21.3 will produce a spectrum with peak signal-to-noise ratio (at 7000Å) S/N = 10 per 10Å-wide wavelength bin in 4 hours (broken into 8 x 1800s CCD exposures).

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