The Coude Echelle Spectrograph for the Lijiang 1.8m telescope

The Coude Echelle Spectrograph (CES) was originally mounted on Xinglong 2.16 m telescope in 1994. When the High Resolution Fiber-fed Spectrograph (HRS) was commissioned at Xinglong 2.16 m telescope, the red path of CES was moved to Lijiang 1.8 m telescope, following some redesign and reinstallation. The CES of Lijiang 1.8 m telescope has the spectral resolution (R = lambda/Delta lambda) ranging from 20000 to 50000 corresponding to different slit widths. With a 2k x 2k PI CCD, CES has a wavelength coverage between 570 nm to 1030 nm. In particular, the resolution of 37000 at 0.5 mm slit corresponds to 1.3 '' on the sky. The limiting magnitude is V = 11.5 with the use of the tip-tilt feedback system, and the S/N is about 40 for 1 hour exposure at 600 nm (R = 37000). During the installation of CES, the tip-tilt mirror technology had successfully fulfilled high precision guiding and tracking for high resolution spectral observation and significantly improved the observation efficiency.