Friday 7 September 2012

Full Moon - Harvest Moon

Full Moon over the Wolds, from High Hutton

The harvest has been in full swing for weeks now, we're officially in Autumn and the nights are drawing in. Often in September we see a fat full moon hanging on the horizon and call it a 'Harvest Moon' - but what is a Harvest Moon and why does it seem so big?

The Harvest Moon is defined as the full moon closest to the Autumn Equinox, the day when the length of day and night are equal and the sun crosses the celestial equator and heads south for the winter. This year that day is September the 22nd and the nearest full moon falls on September 30th, so the next full moon will be a Harvest Moon.

Full Moon and Pampas Grass, High Hutton
And the size? That's down to something called 'The Moon Illusion'. When the moon is seen near the horizon it often appears to be larger and closer than when it is high up in the sky. The reason is still hotly debated by psychologists; one theory suggests that when we see the moon next to recognizable objects on the horizon (houses, trees etc) we judge the size of the moon to be large and near the those objects, but when the moon is high in the sky we have nothing to compare it to and judge it to be small and distant.

But whatever the reason, get yourself outside on the evening of the 30th of September and enjoy the sight of a big and beautiful Harvest Moon rising over the Wolds.

All material © Philip Stone 2012

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