Shine On Harvest Moon

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With the autumnal equinox set to fall on Sept. 22, the 2013 Harvest Moon will be in full bloom tonight.

The term “Harvest Moon” or “Corn Moon,” is used to describe the full moon that occurs closest to fall’s equinox. For skywatchers in North America, the full moon is expected to rise shortly after sunset (depending on your location) on Sept. 18 and will peak at 7:13 a.m. EDT the next morning.

The Harvest Moon will be especially visible during the overnight hours, even though it won’t actually be “full” until Thursday morning.

As EarthSky explains:

No matter where you are on Earth, this full moon – and every full moon – ascends over your eastern horizon around the time of sunset. It’s always highest in the sky in the middle of the night, when the sun is below your feet. That’s because a full moon is opposite the sun. Being opposite the sun, the moon is showing us its fully lighted hemisphere, or “day” side. That’s what makes the moon look full.

However, the almost full Harvest Moon should also be visible for North American viewers on Thursday night, when the moon will turn full for observers in Asia.

The annual celestial sight was dubbed the “Harvest Moon” because its light allowed farmers in the Northern Hemisphere to harvest their crops for several hours more into the night, Farmers’ Almanac notes.

The Full Pink Moon

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The March 2013 full moon will be out all night on March 26, shining in front of the constellation Virgo the Maiden. 

The moon turns precisely full on March 27 at 9:27 Universal Time (4:27 a.m. CDT in the central U.S.). In North America, that means the moon reaches the crest of full phase in the wee hours before sunrise on March 27. But no matter where you live worldwide, watch for the brilliant lamp of the full moon to light up the nighttime from dusk till dawn. Look for the moon low in the east at dusk – at its highest point in the sky around midnight – and low in the west before the sun comes up.

Photo credit: Aunt Owwee

For the Northern Hemisphere, this is the first full moon of springtime. We in this hemisphere call it the Pink Moon, to celebrate the return of certain wild flowers. Other names are Egg Moon, Sprouting Grass Moon, or Easter Moon. In most years, the Christian celebration of Easter falls on the first Sunday after the first full moon of the Northern Hemisphere spring. So tonight’s Easter Moon heralds the coming of Easter Sunday on March 31, 2013.

In the Southern Hemisphere, this is the first full moon of autumn. It’s the Southern Hemisphere’s Harvest Moon – the closest full moon to the autumn equinox. The Harvest Moon ushers in the year’s longest procession of moonlit nights, because the moon rises fairly soon after sunset for several nights in a row. If you live at middle or far southerly latitudes, look for the moon to shine from dusk till dawn for a few to several days in succession.

The first full moon to follow the March equinox faithfully shines in front of Virgo, the harvest goddess, to signal the change of seasons. Watch the March full moon shine all night from sundown to sunup.

The constellation Virgo. Image credit: Wikipedia

 

Grand Illusion

Have you ever seen a beautiful full moon (like the one we had this past weekend) and tried to take a picture of it?  I have.  Here is the disappointing result.

Why does the moon seem so much smaller in the photograph than it did when I viewed it with my naked eye?

It’s an illusion.  One of the most famous of all illusions. Stated simply, the full moon, when just above the horizon, appears much larger than when it is overhead. Yet the moon, a quarter of a million miles away from the earth, always subtends the same angle wherever it is in the sky, roughly 0.5 degrees.

Even professional photographers fall for this one. Many photographs that you see in magazines, containing both a moon and a landscape, will be composites. The landscape will be taken with a normal lens, the moon taken with a telephoto lens, to get a bigger image.

How does this illusion come about? Since the moon always subtends an angle of 0.5 degrees, the image on the retina must always be the same. Clearly the problem is one of interpretation.

One simple experiment shows this to be so. A full moon just above the horizon will not appear so large to the human eye if a piece of paper is held up to that eye with a hole in it, so that only the moon can be seen through the hole and not the horizon. If the other eye is open at the same time, viewing both the moon and the horizon, the two eyes will each see different sized moons!

The reason is we ‘know’ that a cloud that is overhead will be larger than when it moves towards the horizon. And an airplane that is a mere speck on the horizon becomes large when it is overhead. And we are all familiar with standing under a tree which seems enormous, yet at a couple of hundred paces seems insignificant.

So much of our world is interpreted this way that we are ill-equipped to cope with an object like the moon, that subtends the same angle at the eye, whatever position it occupies in the sky. And so our brain ‘interprets’ the image that it ‘sees’, and tells us that the moon is larger than it really is.

And isn’t that wonderful??

The Harvest Moon

This weekend brings the beautiful Harvest Moon!

The Harvest Moon is the name for the full moon that is closest to the autumnal equinox, which came on Sept. 22 this year.

Here’s what that means for the non-astronomers among us.

On average, the moon rises about 50 minutes later each day. But when the full moon occurs near the fall equinox, the gaps between moonrises are shorter. For those in the Northern Hemisphere, the moon rises about 30 minutes later each night. This happens before and after the full moon, resulting in three consecutive days of the moon appearing at nearly the same time.

The early evening moonrises means the Moon shines brightly during early evening for several extra days running — traditionally providing welcome light just when busy farmers needed the extra work hours to get in their crops.

The Harvest Moon may look bigger and seem closer, but it’s not. It’s just another Celestial Grand Illusion!