Lunar Disappearing Act

Location, location, location. Last August New England missed a total lunar eclipse because of our geographic position on the Earth's surface. Observers west of the Rockies were better positioned to witness that event. We only saw the first half of the eclipse before the Moon set. Well, now we will have our chance.

On the night of February 20-21, we will have an opportunity to observe a total lunar eclipse in its entirety. And we will not have to stay up until the wee hours of the morning, for totality will be over before 11:00 pm. Now if only the weather will cooperate.

A total lunar eclipse occurs when the Sun, Earth and Moon are in alignment. With the Earth placed in the middle of this celestial configuration, its shadow is projected onto the lunar surface. The duration of such an eclipse, particularly of totality, is determined by how precisely the three bodies are aligned.

We are fortunate that we will be able to observe this total lunar eclipse from start to finish. The eclipse technically begins at 7:35 pm when the Moon slides into the Earth's light penumbral shadow. Though this initial phase is undetectable, as the Moon slides deeper into the penumbral shadow a keen-eyed observer will see a subtle shading of the lunar surface. The Moon will be moving eastward as it encounters the shadow, so the left portion of the lunar surface will slowly begin to darken. It is just prior to the Moon entering the Earth's dark umbral shadow that one notices that the moonlight looks somewhat subdued.

When the Moon enters that dark umbral shadow at 8:43 pm, the partial phase of the eclipse begins. For one hour and 18 minutes the Moon will move deeper and deeper into the dark shadow, generally from left to right. Then at 10:01 pm the Moon will be completely enveloped by the dark shadow and totality begins. Totality will last until 10:52 pm. That's only 51 minutes - a short duration because the Moon will not be passing through the central portion of the shadow. Will this be a dark eclipse? Will the Moon completely vanish from the sky? We'll know by mid-totality at around 10:26 pm.

During those 51 minutes of totality, note the various hues of color on the lunar surface. Enhance your view with binoculars or a small telescope if you have them. The lunar landscape often looks ashen during totality, with subtle copper, orange or red tones scattered about. And the colors often change as totality progresses. So watch carefully. It is truly a beautiful sight to observe.

Totality ends at 10:52 pm when the Moon begins to leave the dark shadow and sunlight returns to its surface. For one hour and 17 minutes the partial phase will continue until the entire Moon is completely illuminated once again, at 12:09 am. For a while the Moon's light will still look somewhat subdued as the Moon will remain within the light penumbral shadow until 1:17 am when the eclipse ends. (In a dark sky you may be able to detect this shadow soon after the partial phase completes. Thereafter the remaining phase will hardly be noticeable at all as the Moon begins to return to full brightness.)

February's eclipse will occur with the Moon well above the horizon, so you shouldn't have too much difficulty finding a good location from which to observe. The event will take place in the constellation of Leo the Lion. Leo's brightest star, Regulus, will be just above the Moon, while salmon-hued Saturn will be below and a short distance to the left.

If the weather is favorable make every effort to observe this beautiful celestial show. The next total lunar eclipse for us New England won't take place until December 20-21, 2010. So make the best of this upcoming opportunity.

Below is a quick glance chart of the important phases of the February 20-21, 2008 total lunar eclipse. All times are Eastern Standard Time and are approximate. I noted several discrepancies of up to a minute among the sources I researched for this article.

• Moon enters penumbra (eclipse begins - not detectable): 7:35 pm
• Moon enters umbra (partial begins): 8:43 pm
• Moon completely within umbra (totality begins): 10:01 pm
• Moon completely within umbra (mid-totality): 10:26 pm
• Moon begins to leaves umbra (totality ends, partial begins): 10:52 pm
• Moon completely leaves umbra (partial ends, penumbral begins) 12:09 am
• Moon leaves penumbra (eclipse ends - not detectable): 1:17 am

Good luck and keep your eyes to the skies.

And remember, Seagrave Observatory is normally open every Saturday night for public viewing, weather permitting of course. However, snow and icy conditions on the property may close the observatory in winter. Please visit our web site at http://www.theskyscrapers.org for information.