Almost have 2½ years passed since the moon plunged completely into the Earth’s shadow. But if you live in Europe, Africa or the eastern half of North America, be sure to circle March 3 on your calendar.
Unlike an eclipse of the sun, which often requires a long journey to the path of totality, those of the moon can be observed from one’s own backyard. The passage of the moon through the Earth’s shadow is equally visible from all places within the hemisphere where the moon is above the local horizon. Moreover, coming as it does early on a Saturday evening, this eclipse should arouse wide interest among tens of millions of people in the Eastern parts of the United States and Canada who can see it during normal waking hours.
Same show for every viewer
Astronomy clubs can alert schools and the media about their eclipse activities and amateur astronomy in general. Why not throw a neighborhood eclipse party?
The beginning and ending of a lunar eclipse happens simultaneously for every viewer, unlike an eclipse of the sun. Hence the simple schedule below holds for all places from where the event is visible (in the Western United States, the moon won't rise until the event is largely over):
Europe and Africa are in the best position; the eclipse will happen during the late-night hours of March 3-4, with the moon high in the sky. The Canadian province of Newfoundland and Labrador will see the moon rise before its entrance into the umbra (6:00 p.m. Newfoundland Time). For the rest of North America, the eclipse already will be in progress when the moon rises.
Unfortunately, for those living in the Western United States and Canada, the eclipse will have mostly ended by the time the moon rises. As a consolation, however, the next total eclipse, on Aug. 27, will favor these locations.
Focusing on eclipse's total phase
For many of us a total eclipse of the moon can be enjoyed purely as a spectacle, a means of appreciating nature in an unfamiliar guise. But many kinds of careful observations can have scientific interest. Even with the unaided eye a lunar eclipse is pleasing to watch, but binoculars will certainly improve the view. For visual observations, a small telescope is recommended. You should use your lowest-power eyepiece.
This week we will concentrate solely on viewing the moon during the total phase of the eclipse. During the 74 minutes the moon is immersed in the Earth’s dark umbral shadow, the big question will be how it appears in the sky. Some eclipses are such a dark blackish-gray that the moon nearly vanishes from view. At other eclipses it may seem to glow like a bright orange ember.
The reason the moon can be seen at all during totality is that sunlight is scattered and refracted around the edge of the Earth by our atmosphere. If an astronaut were standing on the moon’s surface during totality, the sun would be hidden behind a dark Earth, appearing roughly four times larger than the sun and rimmed by a brilliant reddish ring of all the world’s sunrises and sunsets.
How bright this ring around the Earth appears depends on global weather and the amount of dust suspended in the air. A clear atmosphere on Earth means a bright lunar eclipse. But if a major volcanic eruption has recently injected particles into the stratosphere, the eclipse will likely be very dark. No such eruptions have happened in recent years, so the betting is that the moon will appear fairly bright.
Grays and browns, yellows and reds
The moon will track through the northern part of the Earth’s shadow. The moon’s orientation as seen from eastern Canada and the U.S., means its left portion should appear brightest, as that that will be the part of the moon nearest to the shadow’s edge. There may be a gradation in hue between the parts of the disk nearest and farthest from the shadow center.
A careful description of the colors seen on the eclipsed moon and their changes is valuable. The hues depend on the optical equipment used, usually appearing more vivid with the naked eye than in telescopes. The French astronomer Andre Danjon introduced the following five-point scale of lunar luminosity (“L”) to classify eclipses:
- L = 0: Very dark eclipse, moon almost invisible, especially in mid-totality.
- L = 1: Dark eclipse, gray or brownish coloration, details distinguishable only with difficulty.
- L = 2: Deep red or rust-colored eclipse, with a very dark central part in the shadow, and outer edge of the umbra relatively bright.
- L = 3: Brick red eclipse, usually with a bright or yellow rim to the shadow.
- L = 4: Very bright copper-red or orange eclipse, with a bluish very bright shadow rim.
Examine the moon at mid-totality and also near the beginning and end of totality to get an impression of both the inner and outer umbra. In noting an L observation, state the time and optical means used.
At mid-totality, the darkness of the sky is impressive. Faint stars appear, and the surrounding landscape takes on a somber hue. As totality ends, the eastern edge of the moon begins to emerge from the umbra, and the sequence of events repeats in reverse order until the spectacle is over.
Another procedure is to estimate the stellar magnitude of the moon during totality. When it’s faintest, at mid-totality, the moon may be similar in brightness to naked-eye planets or prominent stars. To see the moon and stars as comparable disks, some nearsighted observers need only remove their glasses. Another technique is to view both the eclipsed moon and comparison stars simultaneously through binoculars held backward, so that the large objective lenses are nearest the eyes.
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