High Dispersion Spectrograph (HDS) for the Subaru Telescope

We present the design and performance of the High Dispersion Spectrograph (HDS) of the Subaru Telescope. HDS is an echelle spectrograph located at the Nasmyth focus of the telescope. The collimated beam size is 272 mm, and the echelle is 300 mm by 840 mm in total size (31.6 gr mm(-1), R = 2.8). HDS has two cross-dispersing gratings with 400 gr mm(-1) and 250 gr mm(-1), which are optimized for the blue and red wavelength regions, respectively. The camera is of the catadioptric type system, consisting of three corrector lenses and a mirror. Two EEV-CCD's with 4100 x 2048 pixels and a pixel size of 13.5 mum are used as the detector. A standard configuration with a 0.4 slit gives a spectral resolution of R = 90000, and a narrower slit width enables higher resolution of up to R similar to 160000. The spectrograph has sensitivities from 3000 Angstrom to 1 mum, and one exposure covers a range of 1500-2500 Angstrom, depending on the wavelength region. The throughput of the telescope and the spectrograph, including the efficiency of the detector, is about 13% in 5000-6000 Angstrom and about 8% at 4000 Angstrom. The stability of the spectrograph and scattered light level are also reported.