From Sydney Morning Herald........SYDNEYSIDERS will have a chance this weekend to glimpse the brightest comet in 40 years.

"It's already way brighter than Halley's Comet," its Australian discoverer, the astronomer Rob McNaught, said yesterday.

If the weather behaves, his comet should be visible on the western horizon, just after sunset, on Sunday and Monday.

Although it should still be visible each evening in the coming week, it is tipped to start fading after Monday.

It is the 31st of 32 comets that Mr McNaught, from the Siding Spring Observatory near Coonabarabran, has found in 20 years, and it has surprised scientists by growing unexpectedly bright as it neared the sun, creating a spectacular sight in northern Europe skies.

"I suspect it's bigger than people suspect," he said. Because it is now so close to the sun, it will be visible only for a few minutes after the sun sets at 8.09pm, and will be very low on the horizon. But Nick Lomb, the astronomer at the Powerhouse Museum's Sydney Observatory, said sunlight reflecting off dust in the comet's tail may make it shine as bright as the planet Venus.

Comet watchers need to look from sites with clear views of the western horizon, unhindered by hills, trees or buildings.

On Sunday evening the comet should be visible until it dips below the horizon 23 minutes after sunset. On Monday it will set 39 minutes after the sun. "The best chance to see it will be on Monday night," Dr Lomb said.

Mr McNaught discovered the comet, officially dubbed C/2006 P1 McNaught, in August while using an automated telescope in a NASA-funded project to scan the sky for asteroids approaching Earth's orbit. To the naked eye, his comet would probably look like "a fuzzy star with a tail".

While amateur astronomers would be delighted, he feared the public's appreciation of such "really, really unusual" sights had been numbed by unrealistic Hollywood movies, with things "whizzing across the sky".

After rounding the sun, the comet will head back to the outer solar system: "It will probably come back in millions of years."

Mr McNaught conceded he was "really, really excited" that his discovery looked set to become one of the two or three brightest comets of the past 70 years, "but it has nothing to do with me. It would still be there whether I had observed it or not."