Coude Echelle Spectrometer

Total efficiency
[Total efficiency (end-to-end throughput) of the CES] This figure shows the total efficiency of the CES as a function of wavelength; it is valid for a seeing of 1 arcsec or better. For greater seeing values the instrumental efficiency decreases.

The thin blue line depicts the inferred efficiency accounting for the blaze function of each order; the thick black line is an interpolation of the efficiency measurements made at various blaze wavelengths and thus an upper envelope to the true efficiencies. Vertical dashed red lines mark wavelengths for which signal-to-noise ratio calculations are presented here.

The figure is valid for the high-resolution image slicer. If the medium-resolution or low-resolution slicers are used, the corresponding efficiencies are increased by a factor of 1.2 or 1.25, respectively. This is a consequence of the smaller number of slices and pertaining reflection losses.


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Last update: 16 May 2001 
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