The Super-Blood-Moon Lunar Eclipse

This Sunday evening, 9/27, stargazers will see a rare supermoon lunar eclipse. If you miss it, the next one isn't until 2033! What makes this event so special?

A Full Moon

First, the moon will be full, as it always must be for a lunar eclipse to occur. This is a special full moon, all on its own, because this is the harvest moon. Traditionally, this designation goes to the full moon closest to the autumnal equinox. In two years out of three, the harvest moon appears in September, but every third year it occurs in October.
At this time of year, corn, pumpkins, squash, beans, and wild rice—the chief Native American staples—are ready for gathering; and at the peak of the harvest, farmers could work into the night by the light of this full moon.
Most of the year, the moon rises an average of 50 minutes later each night, but for the few nights around the harvest moon, the moon seems to rise at nearly the same time each night: just 25 to 30 minutes later across the United States, and only 10 to 20 minutes later for much of Canada and Europe.

A Supermoon

Secondly, the full moon will be at its closest to Earth in all of 2015, what is known to astronomers as a perigee moon. In recent years this has become known as a “supermoon.” Perigee (meaning “closest to Earth”) occurs at 10 p.m. EDT, the moon being a mere 222,374 miles (357,877 km) from Earth.
In fact, the human eye can’t detect the 5 percent difference in size between the moon at perigee and the moon at apogee (farthest from Earth), but everyone who looks at the moon Sunday night will swear it looks bigger than usual. Partly that is because, when seen low on the horizon, the human eye and brain combine to create an optical illusion known as the moon illusion, whereby the moon (and other objects) seen close to the horizon seem larger than when seen overhead.
The moon is the same size regardless of how low or high it is above the horizon. To prove this to yourself, cut out a circle just big enough to block the moon at arm's length and use it to see for yourself that its size stays the same as it rises in the sky.
The only noticeable effect of a perigee moon is that the ocean tides will be a bit higher than usual for the day of full moon and the next three days.

A Total Lunar Eclipse

The third, and most important part of this special event, is that we will have a total eclipse of the moon. At most full moons, the sun, Earth and moon line up approximately, but because of the tilt of the moon’s orbit, the moon passes above or below the Earth’s shadow, and avoids being eclipsed.

At certain points in the moon’s orbit, sun, Earth, and moon line up exactly, and the Earth’s shadow falls across the face of the moon, and we have a lunar eclipse. This is what will happen Sunday night.

The moon’s shadow has two parts: a darker inner part called the umbra, and a lighter outer part called the penumbra. This is because the sun is not a point source of light, so its light leaks around the edge of the Earth, and results in an unsharp shadow. In passing through the Earth’s atmosphere, the light turns red or orange, so that the light that actually reaches the moon is tinted by thousands of sunsets and sunrises all around the periphery of the Earth.

One result of these multiple sunrises and sunsets is that the moon during an eclipse is often tinted red, which is the origin of the idea of a lunar eclipse being a “blood moon.” It isn’t a far stretch of the human imagination to turn this “blood moon” into a portent of disaster.

A lot has been made in the media of this eclipse being the fourth event in a foursome of total eclipses known as a “lunar tetrad.” There really is nothing unusual about four lunar eclipses in two years, since we usually average at least two lunar eclipses every year, though not all are total.
In fact, there was no tetrad of total eclipses at all, because the last lunar eclipse, on April 4, was not really a total eclipse. According to the usual way of calculating eclipses, the moon spent only 4 1/2 minutes in the umbral shadow, but recently this calculation method has been corrected, resulting in the April eclipse failing to be total at all.
This Sunday’s lunar eclipse is a true total eclipse, with the moon being in the umbra for a full hour and twenty-two minutes.

When To See It

Observers in eastern and central regions of North America will get to see the whole eclipse; those further west will see the moon rise already partially eclipsed. Observers in Europe and Africa will see the eclipse before dawn on Monday, September 28.
This brings up the question of dates and times, which often causes confusion. Even a usually reliable source like Canada’s Weather Network, got the date of this eclipse wrong.
Officially, mid-eclipse occurs on September 28 at 02:47 Universal Time, which is the same as Greenwich Mean Time (but NOT British Summer Time). Subtracting 4 hours, this places mid-eclipse in the Eastern Daylight Time zone at 10:47 p.m. on the evening of September 27; the date changes at midnight. So be sure you look for the eclipse on Sunday evening. If you wait until Monday evening, you will be a day late.

Here are the important times in Eastern Daylight Time; if you’re using CDT, MDT, or PDT, the times will be earlier by 1, 2, or 3 hours.
08:11:46  Moon enters penumbra
09:07:12  Moon enters outer edge of umbra
10:11:11  Moon completely in umbra
10:47:09  Mid-eclipse
11:23:07  Moon begins to emerge from umbra
12:27:06  Moon completely out of umbra
01:22:33  Moon leaves penumbra
As always, we look forward to your pictures of this beautiful event.

See The Supermoon On Saturday

Youll probably be hearing a lot about a super moon for the next few months. This is not a term that astronomers use, but here are some facts about what will actually be happening.

Full moon is when the sun, Earth, and moon line up with the Earth in the middle. As seen from the surface of the Earth, the moon is fully illuminated. Because it is exactly opposite the sun in the sky, the moon rises in the east just as the sun sets in the west and, roughly 12 hours later, sets in the west just as the sun is rising in the east.

Because the Earth is constantly revolving around the sun and the moon is constantly revolving around the Earth, full moon is an instantaneous event, occurring when the moon is exactly opposite the sun. This week this happens at 2:35 p.m. EDT on Saturday, August 29. 

Full moon occurs this month at 2:35 p.m. EDT on Saturday, August 29. Credit: Starry Night software.

A minute earlier, the moons phase is waxing gibbous, and a minute later it is waning gibbous.

Each full moon occurs roughly 29.53 days after the previous full moon. Roughly because the moons orbit around the Earth is not a perfect circle, but instead is elliptical in shape. The exact time of full moon varies a little bit from month to month.

The most important result of the moons elliptical orbit is that sometimes the moon is closer to the Earth, and sometimes farther away. The time when it is nearest is called perigee and the time when it is farthest is called apogee.

What we are most interested in is perigee, the date and time when the moon is closest to Earth. This month perigee occurs on Sunday, August 30, at 11 a.m. EDT, about 18 hours after full moon. At that time, the moon will be 222,631 miles (358,290 km) away from Earth.

The moon will be closest to the Earth, called perigee, the next morning at 11 a.m. Credit: Starry Night software.

Notice how less than a days change in position makes it clear that the moon is no longer full: you can see that it is lit more from the left side.

Events like full moon and perigee occur at exactly the same time when viewed from anywhere on Earth, even though the local time on the clock may look different. This month both full moon and perigee occur when it is daytime in North America, and the moon is below the horizon. The best time to see the full moon at perigee will be on Saturday evening, August 29. The moon will be a few hours past full, and perigee will be a few hours in the future, but thats the closest we can get this month.

The important thing for astronomers is that the perigee distance is less than 360,000 kilometers. When the moon gets this close, its most important effect on the Earth, the ocean tides, gets stronger. On the day of perigee and the three days following, we will have larger tides than usual.

Looking ahead to next month, full moon will fall on Sunday, September 27 at 10:51 p.m. EDT, and perigee just 51 minutes earlier at 10 p.m. This perigee will be the closest in 2015, 221,753 miles (356,877 km). The result will be the largest full moon of the year, and even larger high tides. Notice that both events happen in the evening when the moon will be well placed in the sky.

The full moon of September is traditionally called the harvest moon, because it rises around sunset on several successive nights, giving farmers extra light in the evening to bring in their harvest.

The September full moon will also pass through the Earths shadow, a total eclipse of the moon, visible on the evening of September 27 in North and South America, and the morning of September 28 in Europe and Africa.

When the moon is close to full, we can see the strong contrast between its grey plains and white mountainous regions, which some people see as the man in the moon and others see as a rabbit.

With the naked eye or a small binocular, you can easily see the three main dark plains on the upper half of the moon, which bear the fanciful names of the Oceanus Procellarum (Ocean of Storms), Mare Serenitatis (Sea of Serenity), and Mare Imbrium (Sea of Rains). These were named before we knew that there were no open bodies of water on the moon, and no atmosphere to cause storms or rains. Look also for the brightest crater on the moon, Tycho, with its beautiful system of rays, cause by material expelled when it was caused by the impact of an asteroid millions of years ago.