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November's total Solar eclipse: after a dry spell of 28 months, observers are again getting ready for a taste of totality.

TOTAL ECLIPSES OF THE SUN are rare events that offer a unique opportunity for ground-based observers to enjoy a spectacular view of the solar corona. The upcoming eclipse in November has a maximum duration exceeding 4 minutes, but, unfortunately, most of the eclipse path is over the Pacific Ocean.

The central eclipse begins at 20:36 Universal Time on November 13th, which is the morning of the 14th in Australia, when the Moon's umbral shadow first touches down about 190 kilometers (120 miles) east of Darwin in Australia's Northern Territory, along the northeastern border of Kakadu National Park. Sweeping east-southeast, the shadow quickly crosses Arnhem Land and the Gulf of Carpentaria. Barely 80 seconds from the beginning of its landfall, the umbra reaches the west coast of Cape York Peninsula in Queensland near the mouth of the Mitchell River delta. At mid-totality here, the Sun's altitude is already 9 [degrees] and the central duration of totality is 1 minute 57 seconds.

The Moon's shadow crosses the entire Cape York Peninsula in just over 100 seconds and reaches the Pacific coast of Queensland at 20:39 UT. The Sun is now 14 [degrees] high and the central duration is 2 minutes 5 seconds. The coastal cities of Port Douglas and Cairns are deep within the umbral path, lying 10 km north and 23 km south of the central line, respectively. Each city will enjoy over 2 minutes of totality. Well known as popular tourist destinations for trips to Australia's Great Barrier Reef, these cities will also be the chief destination of most 2012 eclipse expeditions, since the shadow track through Queensland's interior encounters little more than an occasional cattle ranch.

After leaving Australia, the remaining 93% of the sojourn, the shadow gradually curves to the northeast, where the total eclipse ends at 23:47 UT as the umbra lifts off Earth's surface more than 500 km west of Chile's coast.

Weather Prospects

Cloud cover over Australia is dictated by a location's proximity to the sea, the terrain, the winds of the day, and the state of the oncoming rainy season, locally known as the "wet." Add to these the very early hour of the eclipse, when nighttime influences are fading and sunlight is beginning to warm the land, and it will come as no surprise that the cloud cover is capricious and difficult to outsmart in most regions. Fortunately, Urania, the muse of both meteorology and astronomy, has spared a small part of the continent for the better fortune of eclipse chasers.

At the start of the eclipse track, in the Northern Territory, a quarter century of satellite observations show an average cloudiness of 75% or more for November. Compounding the weather woes are a road network that suffers from considerable delays or even becomes impassable during the wet season, a very sparse population, and the need for special permission to travel into much of the area crossed by the eclipse track. We cannot recommend eclipse viewing here because of the frequency of heavy clouds, but if travel to exotic destinations is your raison d'etre, then the Northern Territory could provide a great adventure.

In Queensland, the lunar shadow encounters gradually improving weather conditions, with lower cloud coverage and fewer rainy days. From a climatological point of view, it's apparent that offshore waters and the immediate beachfront have a lower average cloudiness than any of the inland areas. As such, on average the best eclipse sites umbra's path stretches across the South Pacific with no other landfall. Greatest eclipse occurs at 22:12 UT with the Sun 68 [degrees] above the horizon during 4 minutes 2 seconds of totality. But the nearest land is the North Island of New Zealand some 1,800 km west of the path, making it an unlikely spot for observers. Continuing on its solitary will be right along the Pacific coast.

Clouds increase significantly just inland from the coast, reflecting the tendency for the mountains of the Great Dividing Range to form clouds in the prevailing southeast winds. But the data in the accompanying map apply to the afternoon hours, which are cloudier than those at sunrise. In the early morning, before the Sun has a chance to warm the slopes, this terrain-induced cloudiness will be lower than shown on the map, though still not as good as the coastal strip.

Even on a very sunny morning, there are always patches of cloud on the slopes or lines of cloud offshore. Completely clear skies are rare, which is typical for tropical environments. These cloud patches can be scattered and widely dispersed, or they can cover up to half the sky with a mixture of broken and open cloudiness. They are constantly changing, forming ephemeral holes in the cloud cover that vary at 15-minute intervals. But observers contemplating moving from one spot to another nearby may make the situation worse rather than better. Furthermore, chasing these openings may be nearly impossible, especially at Port Douglas, as large crowds are expected to gather for a Solar Eclipse Marathon scheduled to begin at the moment totality ends.

If heavy clouds are piling up along the coast during the early hours on eclipse day, a better location can probably be found on the western side of the Dividing Range. But the terrain there takes some distance to smooth out, so the topography's cloud-making effects continue for 100 or 150 km beyond the highest coastal peaks. Nevertheless, the ups and downs of air flow across the terrain will open holes in all but the wettest weather, and so when all else is lost, a trip into and across the Dividing Range will offer the best chances for a view of the Sun. But beware--the roads are cut through areas of tall trees and the terrain is rugged, so you will only get a clear view of the lowaltitude Sun from selected locations. Scouting ahead of time is essential.

Perhaps the most promising option in the Outback is to move well behind the high peaks of the Great Dividing Range, to a location near or west of Mount Carbine along the Mulligan Highway. The highway lies in a shallow valley stretching from Mount Molloy to Mount Carbine, with high peaks to the east and lower ones to the west, which afford some protection from moist ocean winds. At Mount Carbine, the Mulligan Highway turns westward and adopts an orientation aligned toward the rising Sun. Along this route, the Sun should be clear of the mountains at eclipse time.

If you're interested in a remote observing site, note that Outback travel is not a task for beginners. The roads are not designed for wet weather and there is a risk that travelers could be held up for days if the rainy season begins early. Experienced guides and a cautious eye on the forecast are highly recommended.

Eclipse Day Strategy

Because of the proximity of an international airport, abundant accommodations, and an infrastructure geared to handle tourism, the area around Cairns and Port Douglas is serving as the focus for many eclipse tours. Although Highway 44 links the two cities with 40 miles of good-condition, two-lane roadway, heavy traffic congestion on eclipse morning may make last-minute moves difficult.

From the area around Cairns, tall hotels and palm trees, coupled with the low altitude of the Sun at totality, demand a viewing location along the waterfront. Unfortunately, Cape Grafton lying to the east will block a view of the Sun at sunrise as well as the first 20 minutes of the partial phases.

North of Cairns there are clear views to the eastern horizon from many good public beaches along Highway 44, but parking is often limited. For those choosing a beach location during the early morning hours on eclipse day, be aware that the new Moon will bring unusual extremes in the tides. An abnormally low tide expected around 3 a.m. will offer large expanses of beachfront that will vanish as a high tide of up to 3 meters (10 feet) peaks around 9 a.m. This could prove disastrous to anyone setting up early near the water's edge.

Recommended locations with shorefront above the high-water mark include Kewarra Beach, Trinity Beach, and Palm Cove. If possible, scout out an observing location a day or two before the eclipse around the time of high tide. Alternatively, there are many agricultural fields within a few miles of the coast that offer good views with low horizons. Although trees will block the start of the partial phases, the Sun should be clear of any foreground objects by the time of totality.

Once again, advanced planning and site reconnaissance several days before the eclipse are critical to finding a good viewing location. Because the eclipse occurs so early in the day, there will be little time to change locations. Furthermore, the anticipated high traffic volume and rapidly changing cloud patterns may make staying put and hoping for the best the preferred strategy on eclipse day.

In spite of the challenges presented by the 2012 event, it is still the most promising total solar eclipse until the great American eclipse on August 21, 2017.

Challenging weather conditions and limited land within the path of totality make the Pacific coast of Queensland the preferred location for eclipse chasers heading to Australia for this coming November's total solar eclipse.

Visit skypub.com/eclipses for articles on viewing and imaging eclipses.

Retired astronomer Fred Espenak masters two eclipse websites (http://eclipse.gsfc.nasa.gov and www.mreclipse.com) and is a coauthor of Totality: Eclipses of the Sun with Mark Littmann and Ken Willcox. Meteorologist Jay Anderson (University of Manitoba, Canada) has written eclipse weather forecasts since 1979 and has journeyed worldwide to confirm his predictions in person.
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Title Annotation:Chasing the Moon's Shadow
Author:Espenak, Fred; Anderson, Jay
Publication:Sky & Telescope
Article Type:Calendar
Geographic Code:1USA
Date:Apr 1, 2012
Words:1628
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