Viewer's Guide to the June 10 Solar Eclipse -- RealityFans

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Date Posted: 04:16:49 06/08/02 Sat
Author: Tweety
Subject: Viewer's Guide to the June 10 Solar Eclipse

Science | Reuters | Space.com | AP

Viewer's Guide to the June 10 Solar Eclipse
Fri Jun 7, 8:31 AM ET

By Joe Rao, SPACE.com

Last December 14, viewers across a large part of North America were able to see the New Moon crossing in front of the Sun, causing a partial solar eclipse. If the weather in your area was unsettled or overcast and prevented your getting a view of the eclipse, you'll get another chance on Monday, June 10, when once again most parts of North America will have an opportunity to watch the Moon partially eclipse the Sun.

Along a very narrow track that averages only about 26 miles in width, the Moon will appear to cross directly in front of the Sun.

However, because the Moon will be a bit farther from Earth than average, the dark disk of the Moon will appear ever-so-slightly smaller than the disk of the Sun, resulting in an annular or "ring" eclipse. In essence, this is really nothing more than a fancy partial eclipse. It will produce a "penny atop a nickel" effect, with the Sun mimicking a blazing ring of light at maximum effect.

Most observers will simply see a partial eclipse, in which it appears a bite has been taken out of the Sun.

Today becomes yesterday

One unusual circumstance of this eclipse is that because the Moon's shadow falls upon the Earth's surface to the west of the International Date Line, the eclipse will begin on Tuesday, June 11th. Then, as the shadow progresses rapidly toward the east, it will cross the Date Line, causing the calendar date of the eclipse to fall back a day to Monday, June 10th.

At its beginning, the track of the annular eclipse will touch down in Indonesia along the north coast of Sulawesi and then race across the Celebes Sea. The eclipse track will then engulf the Indonesian islands of Pulau Sangihe and Kepulauan Talaud and later Saipan and Tinian of the Northern Mariana Islands chain.

The island of Guam will lie about 25 miles south of the eclipse track and will see nearly 98 percent of the Sun's diameter obscured by the passing New Moon.

Thereafter, virtually the all of the remainder of the annular eclipse track falls over open ocean
waters. The track sweeps as close as 1,600 miles to the northwest of Hawaii, but its final landfall doesn't come until practically its endpoint. It will pass about 30 miles south of the southern tip of Baja, Mexico, before finally reaching Mexico's Pacific Coast, less than 20 miles south of Puerto Vallarta.

Although it will be difficult to make scientifically useful observations, if weather conditions are
favorable, properly positioned observers may obtain striking views and photographs of the setting Sun transformed for just over a minute into a striking "ring of fire" above the Pacific Ocean horizon. Cabo Corrientes and El Tuito are inside the track; Llano Grande is very close to its northern edge.

Several seconds later the 9,100-mile long eclipse track finally comes to an end.

The view from the U.S.

Much of North America will see this as a partial solar eclipse. And there will also be locations that will see nothing. If you have an atlas of Canada and the United States, draw a line starting from a point roughly between the cities of Montreal and Quebec and extend it south, to a point just west of Washington, D.C. Continue the line south to Perry, Florida and on into the Gulf of Mexico.

All places to the right (or east) of this line will have no view of any part of the eclipse.

Meanwhile, those localities to the left (or west) of the line will be able to see at least a part of this eclipse near sunset, although the Moon's "bite" out of the lower edge of the Sun will be small. For example, at Columbia, South Carolina, the eclipse will begin at 8:29 p.m. EDT. The eclipse will still be in progress eight minutes later when the Sun sets with only eleven percent of its diameter obscured.

At Pittsburgh, the Moon will manage to cover 22 percent of the Sun's diameter by the time local sunset occurs at 8:54 p.m. EDT. The eclipse will have gotten underway 24 minutes earlier as seen from the Steel City.

As one heads farther west, more and more of the eclipse will be visible before sunset intervenes. Generally speaking, those who live in the Mountain and Pacific Time zones will get an uninterrupted view.

Go West

The farther to the west and south one is, the larger the magnitude of the eclipse will be.

Across the Pacific Northwest and the Great Plains, anywhere from 30 to 60 percent of the Sun's diameter will be obscured. California and the Desert Southwest will be the most favorably situated with anywhere from 60 to 80 percent coverage of the Sun's diameter by the Moon.

Fine examples include San Francisco (72% at 6:16 p.m. PDT); Phoenix (73% at 6:24 p.m. MST); Los Angeles (77% at 6:22 p.m. PDT) and San Diego (80% at 6:24 p.m. PDT). At all of these locations, enough of the Sun will be obscured at maximum eclipse to possibly cause a subtle diminution in the overall illumination of the sky.

In his autobiography "Starlight Nights," Leslie C. Peltier (1900-1980) wrote of his observation of a partial solar eclipse in June 1918. From his Delphos, Ohio home, the eclipse reached 75 percent coverage. When the eclipse reached its peak, Peltier wrote " . . . the nearby fields, the distant vistas, all seemed wrapped in some unearthly early twilight. The sky seemed darker - shadows faint and indistinct. A cool wind, almost chilly had sprung up from the west."

Observers in the Southwest states may want to look for similar effects around the time of maximum eclipse.

For Hawaiians, this will be an event lasting just over two hours from start to finish. At maximum eclipse (2:42 p.m. Hawaii Time) up to 52 percent of the Sun's diameter will be eclipsed.

For Alaska, eclipse coverage will range from only about 10 percent for northernmost locations (such as Barrow), to about 50 percent for the westernmost Aleutian Islands. As will be the case in Hawaii, this will be an early-afternoon affair.

Be careful

Do not look at the eclipse without proper, specially designed eye protection.

Unlike a total eclipse of the Sun, concentrating its excitement into a few fleeting minutes, a partial eclipse can be watched relaxedly from wherever one happens to be. Once proper precautions are taken, observations can be made with the eye, binoculars, or telescopes of any size. However, looking at the Sun is harmful to your eyes at anytime, partial eclipse or otherwise.

Most people are under the mistaken impression that when a solar eclipse is in progress there is something especially insidious about the Sun's light. But the true danger that an eclipse poses is simply that it may induce people to stare at the Sun, something they
wouldn't normally do.

The result can be "eclipse blindness," a serious eye injury that has been recognized at least since the early 1900's. About half of the reported victims of eclipse blindness recover their precious quality of eyesight after a few days or weeks. The other half carries a permanent blurry or blind spot at the center of their vision for the rest of their lives.

Fortunately, public warnings by news media have vastly reduced solar eye injuries at eclipses in the last few decades. After the solar eclipse that crossed the United States on March 7, 1970, no fewer than 245 cases of retinal injury were reported. Of these people, 55 percent suffered permanent impairment of vision.

In contrast, after the solar eclipse of May 30, 1984, Sky & Telescope magazine was able to locate only three cases of eclipse blindness in the entire United States. During any direct observation of the eclipse, your eye must be protected by dense filters from the intense
light and heat of the focused solar rays.

Pinhole camera

By far, the safest way to view a solar eclipse is to construct a "pinhole camera." A pinhole or small opening is used to form an image of the Sun on a screen placed about three feet behind the opening.

Binoculars or a small telescope mounted on a tripod can also be used to project a magnified image of the Sun onto a white card. Just be sure not to look through the binoculars or telescope when they are pointed toward the Sun!

A variation on the pinhole theme is the "pinhole mirror." Cover a pocket-mirror with a piece of paper that has a ?-inch hole punched in it. Open a Sun-facing window and place the covered mirror on the sunlit sill so it reflects a disk of light onto the far wall inside. The disk of light is an image of the Sun's face.

The farther away from the wall is the better; the image will be only one inch across for every 9 feet from the mirror.

Modeling clay works well to hold the mirror in place. Experiment with different-sized holes in the paper. Again, a large hole makes the image bright, but fuzzy, and a small one makes it dim but sharp. Darken the room as much as possible. Be sure to try this out beforehand to make sure the mirror's optical quality is good enough to project a clean, round image. Of course, don't let anyone look at the Sun in the mirror. [More on this]

Filters

Acceptable filters for unaided visual solar observations include aluminized Mylar. Some astronomy dealers carry Mylar filter material specially designed for solar observing.

Also acceptable is shade 14 arc-welder's glass, available for just a few of dollars at welding supply shops. It also used to be widely advertised that two layers of fully exposed and developed black-and-white negative film was safe. This is still true but only if the film contains an emulsion of silver particles. But beware: some black-and-white films now use black dye, which is no longer safe. It is always a good idea to test your filters and/or observing techniques before eclipse day.

Unacceptable filters include sunglasses, color film negatives, black-and-white film that contains no silver, photographic neutral-density filters, and polarizing filters. Although these materials have very low visible-light transmittance levels, they transmit an unacceptably high level of near-infrared radiation that can cause a thermal retinal burn.

The fact that the Sun appears dim, or that you feel no discomfort when looking at the Sun through the filter, is no guarantee that your eyes are safe.

Future eclipses

The next solar eclipse is scheduled to occur late this year on Dec. 4. It will be a total eclipse with a duration of just over two minutes that will sweep across parts of southern Africa and south Australia.

Interestingly, the next two partial solar eclipses visible over North America will strongly favor Alaska. On May 30, 2003, Alaska and parts of adjacent northwest Canada will see 50 to 80 percent coverage at around local sunset. Then, on October 13, 2004, a large partial solar eclipse will take over western Alaska, again at sunset. Near the town of Kenai (southwest of Anchorage), nearly 93 percent of the Sun will be eclipsed.

But the next time a solar eclipse will be visible over a large swath of North America (as will be the case this coming Monday), won't come again until May 20, 2012, when the path of an annular solar eclipse passes across portions of eight southwestern states.

* * *

Joe Rao serves as an instructor and guest lecturer at New York's Hayden Planetarium. He writes about astronomy for The New York Times and other publications, and he is also an on-camera meteorologist for News 12 Westchester, New York.

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http://story.news.yahoo.com/news?tmpl=story&cid=96&ncid=96&e=1&u=/space/20020607/sc_space/viewer_s_guide_to_the_june_10_solar_eclipse

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Replies:

Thanks Tweety - that's very interesting (NT) -- Cari, 06:32:58 06/08/02 Sat
Absolutely love Space.com -- wedge, 08:17:37 06/08/02 Sat