SALT is modelled on the Hobby-Eberly Telescope
(HET) at McDonald Observatory
, whose innovative design enables it to be built for a fraction of the cost of conventional telescopes. The HET -- and now SALT -- has a spherical array
of 91 identical hexagonal mirror
s of 1m width, which can be produced more easily and cheaply than larger mirrors. SALT's sponsors say the 11m telescope, with an expected life of 50 years, will be built for the same price as a 4m conventional telescope.
The trade-off is flexibility: where conventional telescopes can track the object being observed, SALT's primary mirror will remain fixed at an angle of 37 degrees
to the horizontal. To follow a star's movements over a
period of 48 minutes to two hours, the imaging instruments
will move across a square 12 degrees wide. Distortions introduced by the spherical mirror will be eliminated by four additional mirrors called a "spherical aberration corrector". The telescope will be powerful enough to register the light of a candle flame on the moon.
Sutherland is a remote town in South Africa's semi-desert Karoo region: its clear, dark skies make it an ideal astronomical research site and the town hopes SALT and the associated visitors' centre will attract tourists and much-needed additional income.