Much of what can be done with ISIS should be possible with FOS, with
the same advantages of the waveplates that work for ISIS. Refocusing
FOS for the calcite slab analyser may be involved in some
applications; this can be done, but is not trivial. The Polaroid
analyser can probably be used without refocusing, but requires
``telescope chopping''. It should be possible to mount an analyser
(Polaroid or thin calcite slab) in the multi-slit unit for survey
work. All of this needs development before it can be used.
Our report on the February 1991 commissioning run contains the
following statement (which we still believe to be true): ``FOS has
been proved to give good polarization spectra without refocusing (mode
without FOS lens, first order only). This means that, as with ISIS,
polarimetry can be done with FOS in the course of a normal
spectroscopic run. Interest within the community should be sounded for
partaking in a commissioning run on this option, particularly for
multi-slit applications, for which the useful field is about 35 x 8 mm
(150 x 36 arcsec)". Any offers? Email to: TINBERGEN@HRDKSW5.