Professor Fred Watson

With astronomy, your capacity to gather light is of the utmost importance.

So size matters, and that size is really in the size of the telescopes, the diameters of the mirrors, the bigger your telescope, the fainter the objects that you can detect.

And that's why there is always a drive

to make bigger and bigger telescopes.

In the amateur astronomy community, it has a name.

It's called aperture fever.

You always want the next biggest telescopes with which to explore the skies.

And I'm afraid astronomers in the professional community suffer from the same thing, but it's very, very well directed.

It's because often you are observing things.

For example, with the Anglo-Australian telescope, 3.9 metre diameter mirror,

We have done extraordinary work with that telescope in the 51 years that it's been operational, and often that work is right at the limit of what its capabilities are because of the size of its mirror.

And so you always want the next biggest.

We now live in an era of what are called eight metre class telescopes, of which there are several around the world.

And we're now looking at ELTs, extremely large telescopes with mirrors bigger than 20 metres.

The only one on the horizon is really the ELT.

That's the only one with a firm completion date.

There are two more whose futures are very much in doubt.

So that's the push for bigger telescopes.

But if you build a big telescope and put it in Australia, you're putting it at the bottom of an atmosphere that is really quite turbulent, even at Siding Spring Observatory, which is one of the best sites in the country for doing astronomy.

Part of the issue is to have a dark sky, you need somewhere well away from city lights, but you also need this exquisite stability of the atmosphere that only comes in very dry climates and the top of high mountains.