This week in the Bay of Plenty residents have spotted two suns rolling over the horizon, which WeatherWatch.co.nz calls "an awesome and very rare" optical illusion.

'Mirages appear when particles in the atmosphere refract, or bend light – and this often occurs as the sun is rising or setting through a ‘thicker' atmosphere”, says WeatherWatch.co.nz head forecaster Philip Duncan.

'In 16+ years of running WeatherWatch.co.nz we have never had a photo of a double-sun like this one, it's very cool."

Angel Townend, who took the picture earlier this week, says the photos don't "capture the symmetry or separation of the two [suns]" which they could see with the naked eye.

The Katikati resident took the photo on Tuesday, June 20, from rural town looking out over the Pacific Ocean at about 7.32am.

'Optical illusions are most common in the mornings and evening as the sun shines through a thicker layer of earth's atmosphere," says Phillip.

'The dust, gases and particles can twist light in ways that don't always make immediate sense – but many of us have seen the sun ‘kissing' the sea at sunrise/sunset (where it does a bit of a figure-8 shape) – this is basically another version of that”.