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Multi-Object Spectroscopy

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The multi-object mode of GMOS offers the possibility of obtaining spectra of several hundred objects simultaneously. The GMOS MOS design is based upon precisely fabricating and locating a plate containing many small slits within the spectrograph's entrance aperture. With a 5.5 square arcmin field of view, 30-60 slits can typically be located in a single mask, with a maximum of several hundred slits when narrow-band filters are used. A total of 9 MOS masks (plus the IFU) can be loaded into GMOS at any given time (maximum of 18 MOS masks in very exceptional cases, requiring to remove longlist masks). Actual mask production is done with a laser milling machine located in La Serena. Currently this laser milling machine produces masks for both GMOSs at Gemini North and Gemini South.

Currently offered capabilities:

  • Slit widths 0.5 arcsec or larger
  • Masks designed from GMOS direct imaging
  • Masks designed from object catalogs

See information about:


Gemini Observatory Participants