Construction and commissioning of LAMOST low resolution spectrographs

There are 16 low resolution multi-objects fiber-fed spectrographs (LRS) for the LAMOST project. The spectrographs are of double-beam full Schmidt design by using volume phase holographic gratings. Each spectrograph will be accommodating 250 fibers of 320 micron in diameter which corresponds 3.3 arcsec. The 200 mm diameter collimated beam is split into two separate channels by a clichroic filter. The blue channel is optimized for 370–590 nm, and the red channel for 570–900 nm. Spectra are focused onto 4 K×4 K CCD using fast camera with focal ratio of 1.25. The spectrum resolution is 1000 for low resolution mode. Resolution of 5000 is available by automatic switching to different gratings and by changing camera working angles. The resolution could be doubled by restricting the width of a slit to half the size of fiber diameter. These spectrographs are installed under focal plane of LAMOST at Xinglong observatory. Some of the results obtained during commissioning period are reported.