We estimated total throughput under the following assumptions: a 1% efficiency
loss at each coated air-glass interface, a 2% (or 8%) at each multilayer (or
protected SiO Al) coated mirror reflection. Echelle efficiency has been
estimated from similar R4 echelle gratings (e.g., UVES 31.6 gr/mm grating).
Prism efficiency takes into account internal losses and air-glass interface
losses. Total fiber efficiency includes entrance and exit losses, slit losses,
fiber transmission. The calculations have been carried out at four different
wavelengths (400, 450, 500, 700 nm). Results are shown in table 2.2.
In standard observing conditions (seeing 2 arcsec, sky background V20), limiting magnitudes at R=28000 for 1 hr exposure are V12.5 and 16.5 at signal-to-noise ratio 100 and 10 per resolution element, respectively.