Total solar eclipse underway as thousands converge

A solar eclipse that will turn day into night on Western Australia's North West Cape has started, as thousands gather to witness the rare celestial event.

The eclipse will last about three hours while the moon passes between the sun and earth as a partial then total eclipse, casting a 40km wide shadow over the World Heritage-listed Ningaloo reef region.

Darkness is expected to fall across the North West Cape about 11.29am AWST (1.29pm AEST) when the moon completely blocks the sun.

During that time, a bright solar corona that looks like a white halo may become visible to people in the path of totality, along with some stars and planets.

Astrophysicist Melanie Johnston-Hollitt has always wanted to experience a total solar eclipse and never been in the right place at the right time. 

"To be able to see it from Australia makes it particularly special," she said.

Cruise passengers are taking in the event on a ship anchored off Exmouth, while eclipse goers lining the road to the main viewing point at Cape Range National Park have set up their spots. 

Prof Johnston-Hollitt said the eclipse would help people understand the structure of the solar system.

"We are on a rock, the earth, being orbited by another rock, the moon, both of which are orbiting a star, the sun, in the vastness of space," she said.

The air temperature is also likely to drop during totality and animals may change their behaviour.  

Wildlife biologist Bill Bateman said animals often react to the dimming of the sun as if it were an unexpected sunset and the end of the day.

"Birds may stop singing and move to roosting sites, lizards may move to night-time cover," he said.

Veteran astrophotographer and eclipse chaser Terry Cuttle has six cameras pointing skyward to record the spectacle.

"Two or three minutes before the total eclipse you see the shadow of the moon coming," he said.

"It can look like a really ominous threatening thunderstorm but it's completely silent ... It's awesome ... Then, within a couple of minutes, the sun disappears."

Mr Cuttle said in the last seconds the sun's rays shine over the edge of the moon through valleys, creating an effect called "a diamond ring".

"Then the moon completely covers the sun and you get to see the sun's outer atmosphere ... It streams out from the sun in the shape of the sun's magnetic field," he said.

Thursday's eclipse is also considered rare because it's a hybrid eclipse that starts as an annular eclipse in the Indian Ocean before changing into a total eclipse near Exmouth.

The town, which normally has a population of about 2800, has swollen in recent days, with thousands of visitors keen to witness the eclipse arriving by air and road.

Campsites have sprung up in front yards and on vacant blocks of land and the streets are bumper to bumper with 4WDs and camper vans.

Exmouth's Earlybird Cafe had a line of customers out the door on Thursday morning. 

Owner Mandy Brendel said the influx of visitors had kept her and three staff busy in the lead-up to the eclipse. 

"It's been absolutely amazing," she said while making coffee.

A festival atmosphere has taken hold, with concerts and events at towns and cattle stations across the region.

Australians can also see the phenomena at various times of the day as a partial solar eclipse, with 77 per cent of the sun covered by the moon in Perth, 19 per cent in Sydney, 21 per cent in Melbourne and 27 per cent in Brisbane.