Fig.1a. The optical layout of the echelle spectrometer NES (the plane view):

• S - slit unit;
• M1, M2, M3 - collimator's mirrors;
• E - mosaic echelle;
• G - cross dispersion grating;
• O - camera;
• D1 - CCD.

Fig.1b. The optical layout of the echelle spectrometer NES (the side view).

The layout of the preslit unit is presented here