  The Wide-Field Spectroscopic Telescope (WST) is a concept for a 12-m class
seeing-limited telescope providing two concentric fields of view for
simultaneous Multi-Object Spectroscopy and Integral Field Spectroscopy. The
specified wavelength range is 0.35-1.6 microns. The baseline optical design
relies on a corrected Cassegrain solution feeding Multi-Object spectrographs
through fibres, while the central area of the field is propagated down to a
gravity-stable Integral Field Station housing 144 spectrographs. The Cassegrain
corrector also provides for atmospheric dispersion compensation. All optical
components are within commercially available dimensions. With a view to
minimizing risks and costs, to the maximum possible extent the telescope relies
on proven subsystem solutions. An exception is the tip-tilt secondary mirror,
which would likely have to provide some rejection of wind shake. An iteration
of the optical design is ongoing, with a view to mitigating the weaknesses of
the first baseline design. The telescope would be wavefront-controlled on-sky
at the common-path MOS focus. Controls in the IFS path will need to compensate
for the effect of subsequent differentials - wavefront and line of sight. There
is no shortage of degrees of freedom and metrology solution to do so. The size
of the dome is driven by the Nasmyth footprint and the height of the pier,
which houses the IFS station. The baseline assumption is that a VLT-like
enclosure would provide suitable shielding and ventilation.
