Moon's curtain call: Eclipse on March 3

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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.

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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.

Breathtaking darkness
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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