ARES is the optical spectrograph (designed by Fractal SLNE) currently starting the commissionning phase at the TJO. It is mainly conceived to perform medium-resolution spectroscopy with the following characteristics:

  • Limit star magnitude: S/N=10 for V=13 mag in one hour.
  • Global trasmissivity: > 10%
  • Spectral resolution: R=12000
  • Two spectral windows:

    • Green: between 495 and 529 nm
    • Red: between 634 and 678 nm.

In order to achieve the high global transmissivity (>10%) two telescopes (manufactured by Takahashi) and two VPH are placed in Littrow configuration.


The ARES spectrograph dispersion system is composed by two VPHs developed by Wasatch Photonics, providing the two spectral windows and maintaining the high overall throughput. Both VPHs are mounted on a carriage (prepared to hold up to three VPHs), allowing a fast change from one VPH to the other.

CCD Detector

The detector used is an Andor Technology CCD Newton DU940P camera with the following features:

  • Sensor type: BV- Back Illuminated CCD, VIS optimized
  • Active pixels: 2048 x 512
  • Pixel sixe: 13.5 x 13.5 µm
  • Image area: 26.7 x 6.9 mm
  • Maximum cooling: -100ºC
  • Read-out noise: as low as 2.8 electrons
  • Dark current: as low as 0.0002 e-/pixel/sec
  • Linearity: better than 99%

Generalitat de CatalunyaUniversitat de BarcelonaUniversitat Autònoma de BarcelonaUniversitat Politècnica de CatalunyaConsejo Superior de Investigaciones CientíficasCentres de Recerca de Catalunya