This Monday night (December 20) at midnight, we’ll see the highest Full Moon until 2020. But we must wait ‘til 1:32 a.m. for the eclipse’s umbral beginning – when the first “bite” gets taken from the Moon. Watch as the intense full moonlight flooding the countryside and obliterating all but the brightest stars gets cranked way down – especially after totality starts at 2:40.
Earth’s shadow is usually red. So the Moon becomes a copper phantom when fully immersed. Yet the initial “bite” as the event begins always looks inky-black. Culprit: Our retinas. When the sunlit portion of the Moon is still fat and brilliant, our eyes underexpose the shadowed part. As you watch the eclipse progress, it’s fun to note when the ebony starts becoming reddish: about halfway through.
The eclipsed Moon doesn’t have to be red. It can be pale pink or beige – or even black, so that it vanishes altogether. It all depends on clouds and dust around Earth’s limb. This is the only occasion when a celestial body gives us a report card about ourselves. Coppery-red means that everything is normal. Black means that the dust from the Iceland volcano (and perhaps Chinese pollution) has dirtied our air big-time. Green means that you didn’t set the alarm and are dreaming the whole thing.
As for equipment, a lunar eclipse looks best with either the naked eye alone or else a pair of image-stabilized binoculars.
The Moon will occupy a very special place in the heavens that night. Our sky is a carnival of intersecting planes. There is the flat plane of our solar system seen edgewise, defined by the Zodiac. Then there is our galaxy’s disc, the Milky Way. These eternal planes meet and cross at the Taurus/Gemini border. Astoundingly, a third plane, the solstitial colure – the sky-circling meridian running through the celestial poles in the precise direction of Earth’s tilt – is right there too. It’s an implausible three-way intersection. And yet that – within a few degrees – is where the eclipsed Moon stands that night.
So the Full Moon is eclipsed while aligned with the galaxy’s plane, Earth’s tilt axis and the centerline of our solar system all at once. Are you kidding? The Maya priests would have tossed extra people.
Can you imagine the uproar from the paranoid and gullible if this notable display had coincided with the Mayan calendar flip? Then they’d be sure that it’s Armageddon-time. Happily, no eclipse or conjunction will occur two years from now, on December 21, 2012.
One more thing: The Full Moon’s hot surface aims infrared radiation our way like a bathroom heater. This makes Earth’s lower atmosphere four-100ths of a degree warmer whenever the Moon is full. Will we lose this warmth during the eclipse? I don’t know. Let’s bring along a high-tech lab thermometer that night and really puzzle onlookers.
Wait a minute: onlookers? After midnight in December? No, you and I might just be alone for this one. You will be watching, right?