'Supermoon' looms large in night sky

A massive 'supermoon' will appear in tonight's skies, with scientists advising it'll appear 14 to 15 per cent bigger and about 30 per cent brighter than normal.

Sydney Observatory education officer Geoffrey Wyatt says supermoons occur when Earth's celestial neighbour comes up to 50-thousand kilometres closer to us thanks to its elliptical orbit.

Mr Wyatt says unusually, the next two full moons are supermoons as well, occurring on August 10, which he says will be the pick of the bunch, and September 9.