Wednesday, February 25, 2009

I see a red moon rising: rare natural phenomena captured on camera

Stunning pictures of a red rising moon have emerged today.

The rare natural phenomena, which is known as ‘Etruscan Vase’, is caused by differences in air temperature near the earth's surface.

Also known as an Omega moon because of its shape, the optical effect is more usually seen in views of the setting sun rather than the rising full moon.

Photographer John Stetson caught the moment on camera at Casco Bay near Cape Elizabeth in Maine, USA, earlier this month.

Mirages such as this are possible when there is a layer of relatively warm air at the ocean surface with colder air above it, with a rapid drop in temperature the higher above surface.

On the day the pictures were taken the water was 39F (4C) while the air well above it was a chilly 18F (-8C).

Light passing through the atmosphere bends away from the warmer air towards the colder, denser air.

The result is that we see two moons - one being a mirror image of the other.

The lower part of the image is formed by rays from the moon which are reflected upwards from the warm layer of air at the surface.

If you are above this layer, you see both images together as rays also pass relatively undeflected over the top of the warm layer.

Optics expert Les Cowley said: ‘The effect is not dissimilar to the mirage seen above a hot road surface.

‘The mirage depends on your height above the sea surface. You must be above the warm air layer but climb too high and the effects diminish.’

The moon appears red in colour because it is low in the sky, and blue light from it is scattered by the atmosphere while more red light passes through.

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