IF you are a bit of a stargazer, there will be a very good reason for cranking your neck on Friday night.

Jupiter, Venus and Mercury will line up in the night's sky to form a cosmic trio in the low western sky for half an hour after sunset.

The three planets will be within five degrees of each other - equal to the width of three middle fingers held at arm's length - for the next five days.

According to experts, this will be the tightest group of three naked-eye planets that skywatchers will see until 2016.

Meanwhile, as the planets continue on their orbit path, they will form an equilateral triangle on Sunday night with all three being about two degrees of each other.

According to the Sydney Observatory, unfortunately, this 'planet dance' takes place during twilight and very close to the north-west horizon.

Venus should be visible to the unaided eye from the start of civil twilight, which is about half an hour after sunset.

Binoculars should make Jupiter and Venus visible as well.

For diagrams and other useful information, go to the Sydney Observatory website.

Don't forget, if you get a picture of the show, share with us via our Share a Photo function.