The High Dispersion Spectrograph (HDS), which is located at the Optical Nasmyth platform, provides optical spectroscopy in the range 3 000 - 10 000 Angstroms, with a spectral resolution of up to 160 000; this is the highest resolution of any optical spectrograph on an 8-10m class telescope.

Incoming light is reflected from the slit into a slit viewing camera, while that which passes through the slit is collimated into a 272 mm-diameter beam and dispersed with an 31.6 lines/mm echelle blazed at 71.3 degrees. The light then passes to the cross-disperser, before being focused onto the detector - a 2x1 mosaic of EEV CCDs. One of the cross-dispersers - one for the blue region (400 lines/mm, blazed at 4150A) and one for the red region (250 lines/mm, blazed at 7000A) - is selected according to the user's choice.

The 13.5um pixel size provides a maximum (2-pixel FWHM) resolution of 160 000 (1.8 km/s), which can be achieved with a 0.2'' slit.

Inside of HDS spectrograph room

A new IS #3 with a 0''.2×3 slice pattern, which achieves the highest spectral resolution R=165000, will be avairable in a shared-risk mode from S14A. Please see this page for more detail.

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Outside Link


When referring to HDS in a paper, please use the following citation.

Further information

Questions regarding HDS should be directed to Akito Tajitsu (tajitsu__at__naoj.org).

10 Aug 2017

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