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Spectroscopy

GRACES performs high-resolution echelle spectroscopy between 400 and 1,000 nm. It is offered in two spectroscopic modes.

 

  • 1-fiber (object-only) mode, in which we only collect the spectrum of the star and neglect that from the background sky. The image of the single fiber is sliced in 6 at the spectrograph entrance, which provides an average spectral resolution of R~50,000 (as estimated before commissioning). It is recommended mode for brightest targets (Vmag values still unknown) that outshine the sky background.

  • 2-fiber (object+sky) mode, in which the spectrum of the star and of the background sky are recorded simultaneously on the CCD (with orders interleaved). The image of the two fibers are sliced in 3 each at the spectrograph entrance, which provides an average spectral resolution of R~30,000 (as estimated before commissioning).

 

Most of the "work" is done by the ESPaDOnS spectrograph. The Gemini user has to choose a spectroscopic mode, and to prepare the acquisition. The acquisition is done using GMOS imaging mode. See the following pages for more details.