The Harvest Moon is here, so what’s all the hype about?

It is the timing of moonrise just after sunset that makes the Harvest Moon a spectacular sight. You may have even caught a glimpse of the waxing gibbous moon last night near the horizon, it was huge! The full moon rises above the horizon shortly after sunset (sunset in DC is 6:44 PM, Moonrise is 7:04 PM). The moon will appear bigger than normal when it is near the horizon because of an illusion, or trick your mind is playing on your eyes, known as the Moon Illusion. There are many different explanations o he Moon Illusion including the Ponzo illusion and the relative size theory.

If the sky is clear (which unfortunately may not be the case for the DC area tonight) the view can be superb, but don’t confuse this with a supermoon! A supermoon is something completely different. This is when the moon makes its closest approach to the earth within its orbit (perigee), this will occur on October 9th this month. A moon close to the horizon will look much bigger than a supermoon.

The full moon will not only look big, but it will have an orange hue as well during moonrise and moonset. This occurs for similar reasons why sunsets often look reddish. As we look at moon on the horizon it is at a lower angle than when we look at it higher in the sky. During this, we look are looking into more of the atmosphere or for a greater distance. Blue color has a much shorter wavelength than red and orange The short wavelength colors will be scattered easily and we are unable to see the blueish colors. On the contrary, red and orange have a longer wavelength and they will be the few colors our eyes are able to see during this time.

The Harvest Moon, which is usually in September, is the Full Moon closest to the Autumnal Equinox (September 22). The last time the Harvest Moon fell in October was 2009. The Harvest Moon name was generated around the timing of moonrise just after sunset. This allowed an extended period of natural light to farmers to gather crops.

For the latest forecast for tonight's full moon, click here.