Harvest Moon Eclipse

Total lunar eclipse of April 15, 2014 (credit: Alfredo Garcia, Jr.)

Total lunar eclipse of April 15, 2014 (credit: Alfredo Garcia, Jr.)

On the night and morning of September 27-28, 2015, skywatchers will enjoy a total lunar eclipse at Harvest Moon, the first full Moon of northern autumn. This eclipse will be particularly striking because it peaks just an hour after the Moon makes its closest monthly approach to Earth, so it will appear 13% larger than the last total lunar eclipse on April 4, 2015. This “supermoon” eclipse will be visible for all of North and South America, western Europe, and western Africa. From extreme western North America, the Moon will rise during the eclipse. From South Africa, the Moon will set during the eclipse. For observers in Australia and New Zealand, the eclipse will not be visible.

During a lunar eclipse, the Moon passes into the Earth’s shadow. But it doesn’t go completely dark. That’s because the Sun’s light is refracted and scattered forward through our atmosphere and onto the Moon’s surface. Red light scatters least, so the Moon often takes on a striking dull red or copper color during a total lunar eclipse.

The geometry of a lunar eclipse (credit: Wikipedia commons)

The geometry of a lunar eclipse (credit: Wikipedia commons)

The September 27 eclipse will be the fourth and last eclipse of a tetrad, a series of four consecutive total lunar eclipses over two years. The first three were on April 15 and October 8 in 2014, and April 4, 2015. During this final eclipse of the tetrad, the Moon will appear nearly 13% larger than the total lunar eclipse of April 4, 2015, which occurred when the Moon was at its furthest from Earth.

The April 4 eclipse lasted less than five minutes, but the September 27-28 “supermoon” eclipse will last some 72 minutes. The Moon enters the umbra, the darkest part of the Earth’s shadow, at 1:07 UT. The Moon is totally in the shadow by 2:11 UT, then reaches totality at 02:48 UT. The total eclipse ends at 3:23 UT.

(Note: UT, or Universal Coordinated Time, is the same as GMT or Greenwich Mean Time. You can translate to your own local time at this link).

Some call the reddened Full Moon at eclipse a “Blood Moon”. Since this eclipse occurs at a “supermoon”, some may no doubt call this a “Blood supermoon”. But whatever you call it, this will be an event to remember. You don’t need any optics to see the eclipse, though binoculars will give you a bigger view of the Moon, and a telescope will let you see the eclipse fall over the craters, mountains, valleys, and other surface features of the Moon.

A total lunar eclipse is also a photogenic target, especially when the Moon is fully inside the umbra and appears coppery red. Nearly any camera that lets you set the exposure manually will do a good job. Unless you have a telephoto lens with 200-300 mm focal length, it will be hard to get a close-up of the lunar disk. Instead, use a focal length of 35 mm to 135 mm, roughly, and frame the Moon, if possible, with terrestrial objects like trees, mountains, houses, and so forth. The disk will look small but colorful. Set the f-stop to its fastest, somewhere between f/1.8 to f/3.5 or f/5.6. Use an ISO of 400-1600. And experiment with the exposure time to suit your conditions. Try 1/2 second to 15 second and see what works best. A camera tripod is a must.

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