June 15th's Deep, Eastern Lunar Eclipse

We're in the midst of an interesting eclipse trifecta. Partial solar eclipses occur during the New Moons on June 1st and July 1st, which are sandwiched around a total lunar eclipse during the Full Moon on June 15th.

Unfortunately, none of these are really visible from North America — which is too bad, because this lunar eclipse should be a doozy. Those of you in Europe and elsewhere in the Eastern Hemisphere are in for a real treat.

The Moon will plunge deeply into Earth's shadow, passing almost directly through its center. Consequently, totality lasts a whopping 100 minutes — the longest umbral immersion since July 2000, and nearly 40 minutes longer than the well-observed lunar eclipse last December 21st.

The lunar disk first encroaches into the penumbra, Earth's partial shadow, at 17:25 Universal Time, but don't expect to see any dusky shading along its easternmost edge for at least 30 minutes afterward. The first nibble from Earth's deep umbra comes at 18:23 UT, with the black bite taking a full hour to creep steadily across the disk.

Totality begins at 19:22:30 UT and ends at 21:02:42 UT, with the moment of greatest eclipse at 20:12:37 UT.

The long duration of this event is due in part to Earth being near aphelion in its orbit and the Moon being near perigee in its orbit. Since the lunar disk passes 5.3 arcminutes north of the umbra's center, observers might see the northern limb appear a little brighter than the southern limb.

In any case, this has the makings of a very dark eclipse. Observers rate totality's darkness using a five-point scale developed by French astronomer André Danjon, ranging from L = 0 (nearly invisible) to L = 5 (bright copper-red or orange disk). (Click here to learn more about the Danjon scale and other eclipse tips.)

David Dunham points out that the darkened lunar disk makes it very easy to watch the Moon cover up stars along its path. "Especially good will be the occultation of 4.8-magnitude 51 Ophiuchi," he notes. "Perhaps a naked-eye event, it will be spectacular as seen with binoculars or any small telescope." Click here to get a full listing of stars to be occulted during the eclipse.

And for you shutterbugs, JPL investigator Wesley Traub has a special request. He'd like to collect photometrically calibrated images of the lunar disk taken near the time of mid-eclipse, in order to measure the amount of light scattered onto the lunar disk as a function of distance from its center. "My ultimate interest is in getting data that could be useful for interpreting transit experiments on exoplanets," he explains.

(Photometrically calibrated or not, your eclipse shots would make a great addition to Sky & Telescope's online image gallery.)

As the map at right shows, the ringside seats for Wednesday's event will be centered around 50°E in longitude. This favors eastern Africa (near moonrise), Asia, and western Australia (near moonset). Those of you in Europe will see most everything, though the early stages occur before the Moon rises. Only northern Scotland and Scandinavia miss out — but, then again, they were favored for the partial solar eclipse on June 1st.

Those of us stuck in North America won't see any of this eclipse by eyeball, but we'll be able to watch it vicariously thanks to the following live webcasts:

• AstroNation.net from Hessen, Germany
• AstroViten from Oslo, Norway
• Bareket Observatory from Maccabim, Israel
• Ciclope's SkyLive.tv from Tenerife (Canary Islands)
• ECA (Eclipse Chasers Athaenium) from Delhi, India
• Eclipse-Live from Offenburg, Germany
• ServiAstro from Barcelona, Spain
• SLOOH from Tenerife (Canary Islands)
• Sky Watchers Association of North Bengal from Siliguri, India

Later this year, on December 10th, most North Americans will have a chance to see a total lunar eclipse. Let's hope for clear weather!