Users' Manual for the CFHT
Subarcsecond Imaging Spectrograph (SIS)

Christian Vanderriest and David Bohlender

HTML adaptation by David Bohlender

HTML Version 3.20; 15 February 1996

This manual was generated with Nikos Drakos's translator. A hard copy of the manual in its entirety may be obtained by contacting the author or CFHT. Individual sections are also easily printed from your WWW viewer. You can also retrieve and print the postscript version, but be forewarned that the postscript file has a size exceeding 5.0 MB.


Multiplexing is now a common technique for increasing the efficiency of ground-based telescopes. It can make a medium or large aperture telescope more efficient than a very large telescope that lacks this capability. With this in mind, the CFHT's dual Multiple Object and Subarcsecond Imaging Spectrograph (MOS/SIS) was designed for the purpose of offering the best possible multiplexing gain while observing with the 3.6 m CFH telescope.

Another very important parameter for efficient observations is the spatial resolution. With its location at the summit of Mauna Kea, the CFHT is situated at arguably the best site in the world with regard to ``natural seeing''; constant care aimed at preserving the best possible seeing has resulted in an average observed resolution of approximately 0.7" (FWHM). This image quality is further improved with SIS, for direct imaging as well as spectroscopy, by using an active mirror which compensates for image motions at a rate up to 20 Hz. The typical spatial resolution is then boosted to 0.5" - 0.6".

This manual describes the present status of SIS and the observing procedures for using it efficiently. It is provided in order to allow you to prepare observing time proposals and scheduled observations. Critical comments on the manual's contents are welcome and should be directed to the authors or CFHT's Directors. The manual is essentially an updated version of the MOS/SIS manual written by O. LeFèvre. However, we chose to separate MOS and SIS because observers have in fact to deal with either one or the other of these two spectrographs. Moreover, SIS differs even more from MOS now that the OSIS project is nearing completion. Observers interested in using MOS should refer to the ``Users' Manual for the CFHT Multi-Object Imaging Spectrograph (MOS)@'', also written by C. Vanderriest and David Bohlender. The manual also does not cover Fabry-Pérot observing modes. These are described in the ``User's Manual for the Scanning Fabry-Pérot Spectrograph with the MOS/SIS Focal Reducers@'', written by R. Arsenault. The Integral Field Spectroscopy (IFS) mode provided in the MOS-ARGUS configuration will also be covered in a separate manual, to be released soon.

At this time the current manual does NOT include a discussion of the infrared capabilities of OSIS.

Please send comments and suggestions regarding the HTML version of this manual to Christian Veillet.