About the Subaru Telescope

Observational instruments

HDS (High Dispersion Spectrograph)

HDS (High Dispersion Spectrograph)

The High Dispersion Spectrograph provides extremely high spectral resolution observations in visible light. Capable of dividing light into as many as 100,000 different colors and observing them simultaneously, it is notable for its high resolving power in spectroscopy. HDS plays an active role in measuring spectra to indicate the presence of exoplanets as well as to evaluate the abundance of elements in very old stars formed at the beginning of the Universe.

Fast Facts


  • High-dispersion spectrograph
  • Optics composed of 3 corrector lenses and a mirror
  • High spectral resolution (i.e., high dispersion)


  • Often used for the observation of very bright objects
  • Uses a reflective Echelle grating to obtain high spectral resolution.
  • Divides visible light into as many as 100,000 different colors and observes them simultaneously.


  • Understand the chemical evolution of the Universe
  • Analyze the chemical composition of stars, particularly old stars
  • Study distant clouds of gas
  • Search for exoplanets
  • Observe the periodic variation seen in the star's spectra in the Doppler shift (movement of astronomical objects toward or away from Earth), indicating a change in the motion of objects, e.g., the wobble of a star. Changes in the motion of objects, e.g., wobble of a star
  • Estimation of a planet's mass and separation from its star on the basis of data on periodic variation


  • Size and weight
  • Size: 6 x 6 x 3 m
  • Weight: 6 tons
  • Placement:
  • Optical Nasmyth focus, which provides the necessary room and stability for its huge size
  • Permanent installation in a refrigerated container to retain its mechanical and thermal stability
  • Wavelength(s): 0.31-0.93 microns
  • Detectors
  • Two 2048 x 4096 pixel EEV CCD42-80
  • Arranged in a 2 x 1 mosaic
  • Pixel size: 13.5 microns
  • Pixel scale: 0.138"/pixel
  • Field of view: 2-6 arcseconds (slit width)
  • Spectral resolution: 100,000 with maximum resolving power of 160,000


  • 1996 Established basic design in cooperation with Nikon.
  • 1998 Fabrication began.
  • 1999 Installed on the telescope
  • 2000 First light
  • 2001 Open use began in April.
  • 2014 Development of a multi-object unit to place in front of the original slit.

Specialized Information about the Instrument and Observing: