FORS - FOcal Reducer and low dispersion Spectrograph

Summary

FORS FORS is the visual and near UV FOcal Reducer and low dispersion Spectrograph for the Very Large Telescope (VLT) of the European Southern Observatory (ESO). Two versions of FORS have been built, upgraded and moved to the Cassegrain foci of different telescopes in the past years. FORS is designed as an all-dioptric instrument for the wavelength range from 330 nm to 1100 nm and provides an image scale of 0".25/pixel (or 0".125/pixel with the high resolution collimator) in the standard readout mode (2x2 binning). FORS1 is mounted on UT2 (Kueyen) and equipped with a new mosaic of two 2k x 4k E2V CCDs (with 15 μm pixels) optimised for the blue range (<600 nm) while FORS2 is installed on UT1 (Antu) and optimised for the red with a very low level of fringes thanks to a mosaic of two 2k x 4k MIT CCDs (with 15 μm pixels). The geometries of both FORS1 and FORS2 detector systems are very similar: in both cases the detectors are flat and the bottom detector is rotated by 0.08 degrees and shifted by about 30 μm with respect to the upper "master" detector. The gaps between the two detectors are about 480 μm. FORS1 has a polarimetric capability while FORS2 allows multi-object spectroscopy with exchangable masks (MXU) and has a high time resolution mode (HIT mode).

Publications based on data obtained with the FORS instruments should quote the following reference paper: Appenzeller, I. et al. 1998, The Messenger 94, 1.

Important

  • The arrival of X-Shooter in P82 will have an impact on the availability of FORS1, please see the Call for Proposals and the FORS news page for more details.
  • We have successfully completed the blue upgrade of FORS1 on April 6, 2007. The upgrade included the installation of a new CCD mosaic (similar to that of FORS2, but optimized for blue rather than red) and of a new and more efficient set of broad band filters.
    For more information, have a look: here

Contact Information

Content of these pages

The following items are available on all the FORS pages, using the bar on the left.

  • Overview: a short description of the instrument
  • News: list of changes affecting the instrument and/or its pages.
  • Instrument Description: all the important parameters of the instrument.
  • Manuals: links to all the documents related to FORS.
  • Tools: a collection of useful tools and informations for preparing and analyzing the FORS observations.
  • Instrument Operations Team
  • Visitor Instructions: Instrument specific instructions for Visiting Astronomers