High-Resolution Fiber-Fed Spectrograph for the 6-m Telescope of the Special Astrophysical Observatory of the Russian Academy of Sciences: Assessment of Efficiency

Abstract : We report the results of laboratory tests of the first version of the high-resolution fiber-fed spectrograph designed for the Special Astrophysical Observatory of the Russian Academy of Sciences (SAO RAS). During laboratory tests a spectral resolution of about 70 000 was achieved. The peak efficiency of the entire optical path of the spectrograph (without light losses at the CCD, primary mirror of the 6-m telescope, and in the atmosphere) at 620 nm and with the equivalent slit widths of the 1″.5 and 0″.75 are equal to 8% and 4%, respectively. The resolving power R = 70 000 and 100 000 can be reached with the sky aperture 0″.75 and 0″.4 respectively. In the current version of the spectrograph these regimes of operation are implemented by mechanic aperturing of the slit. A dedicated projecting camera has been developed and is currently manufactured to operate with a collimated 200-mm diameter beam, which will make it possible to increase the spectral resolution up to 100 000. A two-beam image slicer will be used to maintain the luminous efficiency of the instrument at least at the 6% level.