Goodman High Throughput Spectrograph

Updated Aug 23, 2016 (César Briceño)

NEW: the mask cutter at Gemini-S/CTIO is again operative. Users requesting the Goodman MOS mode can submit their mask files 1 month in advance of their observing run (see the MOS Slit Design Guide)

The Goodman High Throughput Spectrograph (GTHS) was built in the Goodman Laboratory at the University of North Carolina under the leadership of Prof. J. Christopher Clemens. It is an imaging spectrograph, capable of producing excellent image quality across a 7.2 arcmin diameter FOV (with a 0.15 arcsec/pixel scale), and spectra at various resolutions from the atmospheric UV cutoff all the way out to 850nm. It employs all transmissive optics, and Volume Phase Holographic (VPH) Gratings to achieve the highest possible throughput for low resolution spectroscopy over the 320-850 nm wavelength range. In order to capitalize on the properties of VPH gratings, the instrument features an articulated camera. This allows the camera-collimator angle to be adjusted so as to tune the blaze wavelength, thus maximizing the efficiency at any desired wavelength.  Because VPH gratings operate via Bragg scattering, efficient operation requires Littrow or near-Littrow operation of the spectrograph. A grating rotation stage sets the incident angle to the desired value, which depends upon the line density of the grating and the wavelength of interest.  A concentric camera rotation stage must then be set to nearly twice this angle to intercept the diffracted beam.
  • The GHTS can be used in both single slit and multi-object slit (MOS) mode (see links below).
  • Gratings from 400 to 2400 l/mm are available.
  • An Atmospheric Dispersion Corrector (ADC) is available (controlled by the Telescope Operator, so its use is transparento to the observer). The SOAR ADC is capable of full correction down to elevations of 30 deg above the horizon. Below that, and down to the 15 deg elevation limit of the telescope, the correction will be only partial; however, we recommend avoinding targets at elevations lower than 20 deg.  The ADC is most useful for MOS observations, or when the program does not allow orienting the slit at the paralactic angle.

General Information:

Observing Information and Tutorials:

Calibration Information:

Software for Goodman:

Data Reduction Guides:  coming soon!