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Slit Dimensions

Both GMOSs have a number of 'permanent' masks containing long slits suitable for long-slit spectroscopy. The long slits have various widths ranging from 0.25 arcsec to 5.0 arcsec. The slits have small bridges, approximately 3 arcsec long, to keep the mask flat in the focal plane (see the image in the table below).

Long-slits for both standard and Nod-and-Shuffle observations are also available. The Nod-and-Shuffle slits have lengths of 108 arcsec centered in the field of view. The Nod-and-Shuffle long-slits are available in slit widths of 0.5, 0.75, 1.0, 1.5 and 2.0 arcsec.

If users require slit widths other than the permanent ones listed below, or long-slit masks with holes for alignment objects, such requests will be handled as multi-object spectroscopy and the user should request to use GMOS in MOS mode. The user will have to prepare the masks using the usual mask-making procedure. A total of 18 masks (plus the IFU) can be loaded into GMOS at any given time.

Slit width Slit length(s) Plot
0.25 arcsec 330 arcsec
0.5 arcsec 330 and 108 arcsec GIF image
0.75 arcsec 330 and 108 arcsec
1.0 arcsec 330 and 108 arcsec
1.5 arcsec 330 and 108 arcsec
2.0 arcsec 330 and 108 arcsec
5.0 arcsec 330 arcsec