Instrumental functions of a 5-m echelle spectrometer with diffraction-limited resolving power.

The resolving power R of a 5-m echelle Czerny-Turner spectrometer, designed for the spectral range between approximately 100 nm and approximately 1000 nm, was determined by measuring its instrumental functions using stabilized lasers. At lambda(1,air) = 514.534 nm in 11th order and at lambda(2,air) = 632.819 nm in 9th order the values of the resolving power are R1 = 8.38 x 10(5) +/- 2.5% and R(2) = 7.00 x 10(5) +/- 2.6%, which correspond to 95% or 97% of the theoretical values, respectively. Aberrations, particularly caused by coma as well as by imperfections of the grating and mirrors, are nearly eliminated. The resolving power is limited by diffraction at the aperture stop on the grating.