HIDES: a High Dispersion Echelle Spectrograph

This paper describes a High Dispersion Echelle Spectrograph (HIDES)at the coudé focus of the 188cm ref lector of Okayama Astrophysical Observatory, NAOJ.HIDES uses an echelle grating (31.6gr/mm, R =2.14)as the main disperser.Two reflection gratings with the ruling densities of 400gr/mm and 250g r/mm are used for the post cross-disperser.The camera consists of five spherical lenses, has the aperture of 200mm diameter, and is designed to achieve spot sizes smaller than 15μm within the image circle of 60mm diameter at waveleng ths from 360nm through 900nm without refocusing.A mosaic of two 2K×4K CCDs with 13.5μm pixel from EEV is employed. The large area of the detectors enables to cover the free spectral range of any order without rotating the echelle.The wavelength coverage in a single exposure is about 200nm with the red crossdisperser and mosaiced CCDs.Typical spectral resolution will be 68, 000 with 0.76"slit width. At this resolution one hour exposure will give a detection of a point source at 12-th magnitude at 550nm with the S/N of about 10.