It’s been a bumpy few years for the Southern African Large Telescope (SALT). Despite being one of the newest and most advanced telescopes in the world, it’s been plagued by seemingly endless image quality problems. Those problems have all been largely to do with it having a slightly unusual design. SALT is essentially a bigger, shinier, beefed-up version of the Hobby-Eberly telescope. The segmented mirror and the minimal movement required to acquire and track targets across the sky make for a lower overall cost. Unfortunately, therein lay the problem. The problem with SALT has been a bit like the reason I wear glasses. Astigmatism. And unfortunately, telescopes can’t just go to Specsavers.
No one had ever constructed a telescope quite like SALT before. As with all pioneering projects, SALT had problems. Serious ones. The above image is a snapshot of SALT’s field of view. As you can see, it’s rather a mess. Ranging from the relatively clear top right to the horrifically messy bottom left, this was quite a disappointment for everyone involved.
For some years now, the plucky scientists and engineers at SALT have been working to fix the problems and it’s been quite a mission for them. So much so that there’s an entire blog dedicated to fixing SALT’s image quality problems, charting every milestone since April 2009. Needless to say, I’ve been keeping an eye on their progress from over here.
The good news is this:
Taken on the night of August 27th, a few days ago, this is SALT’s new clean field of view. And isn’t it pretty? This, my friends, is a pristine starfield with virtually no optical distortion. What little astigmatism remains can be cleared up with the relatively simple job of correcting the primary mirror.
In short, SALT is fixed! How exciting!