Partial Solar Eclipse for Alaska
Weather permitting, most Alaskans will see a partial solar eclipse on the evening of July 21 this year. The zone of full lunar shadow, where the moon's disk seems to black out the entire sun, is called the umbra. On the 21st, it will touch Earth at sunrise in Finland, sweep along the arctic coast of Siberia, cross into the North Pacific, and leave at sunset over the ocean between Hawaii and California.
Except for the mid-Aleutians, most of Alaska will lie outside this path of totality. The penumbra--the path of the partial eclipse--will reach more populated parts of the state.
In Fairbanks, people will see a small bite vanishing from the lower edge of the sun beginning at 6:21 p.m. Alaska Daylight Time. The bite will grow, leaving a crescent sun with its horns pointing downward, to a maximum at 7:17 ADT. Nearly three-quarters of the sun will be covered by the moon at that time. The sun's apparent altitude will be 23 degrees above the horizon.
The eclipsed sun will also be 23 degrees high at Anchorage, where the action begins at 6:26 and reaches maximum--a little more than at Fairbanks, with 76 percent of the solar disk covered--at 7:24 ADT. Both cities will be completely out of the eclipse by 8:30, when Kodiak and Juneau should have their best views. Juneau will see less than 70 percent of the sun's face covered, but Kodiak--assuming no clouds intervene--falls right on the 80 percent line, and at 8:30 nearly exactly. Residents of Cold Bay and the Bristol Bay communities should be glancing skyward before then, because their maximum eclipse will come at about the same hour. They'll see either clouds or, with luck, a decreasing crescent sun finally covered slightly more than it appears to be at Kodiak.
This information comes from the July issue of Sky and Telescope magazine, which does not cover many Alaska sites of interest but does have information from which you can calculate the best time for seeing the eclipse at your location. It also contains the standard warning: do not stare at the eclipse with inadequately protected eyes. This warning is important; remember to share it with children! Dark glasses just aren't enough; you need arc-welder's goggles or something similar to prevent eye damage.
I confess, my favorite activity during a partial eclipse doesn't require eye protection; I watch the fantastic shadows cast by a tree with healthy foliage. The effect is of hundreds of pinhole cameras, reproducing the crescent sun on any smooth surface undemeath. So I'll be camped under my favorite aspen, watching tiny snapshots of the eclipse dance and quiver on a ground cloth.
Unfortunately for northerners' egos, one of the articles in the magazine called our impending eclipse a dress rehearsal. Astronomers thinking of eclipses, like seismologists considering earthquakes, are given to speaking of "the big one." Unlike the seismologists worrying about Califomia's fate, though, the astronomers know when their big one will occur: July 11, 1991. Then the moon's shadow will sweep from Hawaii into southem Mexico, skirt the Pacific coast of Central America, then move into northern South America. At the optimum point, totality will last just under seven minutes--quite long for an eclipse.
It's only a trick of geometry that next year's show is taken more seriously by the astronomical community: the longest totalities must occur in the tropics. That is where the bulge of Earth's slightly squashed spherical shape reaches most deeply into the moon's tapering shadow. Next year's eclipse has one more feature in its favor, in that the moon will be close to perigee, the point in its orbit when it comes closest to Earth.
Foo. A trip to the tropics in July seems wrongheaded to me. Besides, aspens don't grow in Hawaii; those astronomers will miss the dancing images of a crescent sun.
