Updated on July 2, 2021, 3:53 am


Download the latest simulator (includes hydraassign):
              Solaris version -- Linux version (updated October 2001)

Latest hydraassign code binary (valid for 2010+, will be placed in the above tarballs) binary code
Replace this in /Hydra/bin/

Get the latest concentricities file:

(NB! Be sure that ECCENFILE in .fiborg points to the right concentricities file)



"Hydra-CTIO" is a multi-object, fiber-fed spectrograph which is used with the CTIO Blanco 4m telescope. The positioner is mounted at the Cassegrain focus, with the fibers feeding a bench spectrograph located in a room below the dome floor. Hydra-CTIO will ultimately be the principal Cassegrain instrument on the 4m telescope.

The instrument was commissioned during October-December, 1998. It was first used with an Air Schmidt camera and Loral CCD. In its current incarnation, Hydra-CTIO uses a 400mm camera and SITe 4Kx2K detector. The new camera/detector combination offers superior resolution and lower dark current compared to the old Air Schmidt. The Loral Air Schmidt is no longer in use.

Hydra-CTIO is similar to Hydra-WIYN, now in routine use at KPNO. A number of upgrades have been made to Hydra-CTIO. Its salient parameters can be summarized as follows:

  • 138 large (300u/2.0" dia.) fibers
  • Spectral coverage 330-1100nm
  • Positioning time ~20 minutes (~8 sec./fiber)
  • 40 arcminute field of view
  • Minimum fiber-fiber distance 25"
  • Atmospheric Dispersion Compensation
  • Slit plates for higher spectral resolution: spectral resolution to ~50000 with the 400mm camera and the narrowest slit plates