Astronomy Blog

SALT mirror completed

Since 2000, the South African Astronomical Observatory (SAAO) have been building the South African Large Telescope (SALT). This is now the largest optical telescope in Africa with a staggering 11m primary mirror (look at the person in the picture to get an idea of the scale). The design is based on the Hobby-Eberly Telescope (HET), in Texas, and is made up of 91 hexagonal mirror segments. I saw the first few segments in place back in 2003 and it has been a delicate job since to put all the segments together. Each segment is 1m across, 100 kg in mass and has to be positioned using special cranes and winches. During installation, the telescope engineers had to be careful not to drop anything!

In May this year the primary mirror construction was completed and SAAO have some pictures of the final stages on their website. The telescope will be inaugurated on 10th November 2005.

The largest telescopes on the planet such as the VLT, SALT and Keck are four to six times the diameter of the HST. Looking ahead twenty years, the next generation will be the extremely large telescopes (ELTs); around 50-100m in diameter. The European large telescope project was previously known as OWL but is now referred to as ELT because the name wasn't considered serious enough.