The University Observatories of München and Göttingen and the Landessternwarte Heidelberg are building in cooperation with ESO two almost identical FOcal Reducer /low-dispersion Spectrographs (FORS) for the ESO Very Large Telescopes. FORS allows low-dispersion multiobject spectroscopy (19 slits) and longslit spectroscopy in the wavelength range of 330 to 1100 nm. A set of standard grisms with reciprocal dispersions of 45 ...230 Å/mm working in the first order are foreseen. With a slitwidth of 1 arcsec the resulting spectral resolutions range from 180 to 1800.
For further FORS details see Appenzeller and Rupprecht (1992) and Seifert et al. (1994).
The standard grisms are located in a grism wheel in the parallel beam between the collimator and the camera. Seven of eight positions are available for grisms. The free diameter of the grisms is 135 mm to cover the whole field of view of FORS. To avoid reflection ghosts the entrance surfaces are all tilted by .