Three types of spectroscopy are possible with each GMOS and its selection of gratings.

• Long-slit spectroscopy, which covers the full extent of the CCD package (3 x 2048 pixels) with two small gaps.
• Multi-object spectroscopy, which uses custom-designed, laser-milled masks.
• Integral field spectroscopy, which uses 0.2 arcsec fibers covering a 35 square arcsec field of view.

Each of these modes has a separate section in the GMOS pages. Only the gratings and filters used by all three modes and the detector properties are described in this section.

The spectral resolving powers available range from about 500 (for the widest slits used on extended objects) to 4400 with a slit width of 0.5 arcsec, and 8800 with the (narrowest) 0.25 arcsec slit. Note that in normal seeing conditions slit losses will be very large for the narrowest slits.

The GMOS gratings exhibit scattered light, the level of which varies with wavelength and grating. Some example spectral images and potential strategies to mitigate the effects of scattered light on science data are given here.

• Camera Properties
• Gratings
• Filters
• Detector
• Scattered Light