Total Eclipse of the Sun 2017

United States #5211 (2017)
United States #5211 (2017)

Monday, August 21, 2017, is ECLIPSE DAY, at least if you reside in the United States of America. A few hours from now as I write this, a total solar eclipse will be visible within a band across the entire contiguous United States. No non-U.S. land will experience totality during this eclipse as it travels across the Pacific Ocean prior to making landfall and following its departure after which it will traverse part of the Atlantic Ocean. The last time a total solar eclipse was visible across the entire contiguous United States was during the June 8, 1918, eclipse and not since the February 1979 eclipse has a total eclipse been visible from anywhere in the mainland United States. The path of totality will touch 14 states (although a partial eclipse will be visible in all fifty states) covering 16% of the area of the nation. The event will begin on the Oregon coast as a partial eclipse at 9:06 a.m. PDT and will end later that day as a partial eclipse along the South Carolina coast at about 4:06 p.m. EDT.

A solar eclipse occurs when the Moon passes between Earth and the Sun, thereby totally or partly obscuring the image of the sun for a viewer on Earth. A total solar eclipse occurs when the moon’s apparent diameter is larger than the sun’s, blocking all direct sunlight, turning day into darkness. Totality occurs in a narrow path across Earth’s surface, with the partial solar eclipse visible over a surrounding region thousands of miles wide.

Today’s total eclipse will have a magnitude of 1.0306 and will be visible within a narrow corridor 70 miles (110 kilometers) wide crossing fourteen states of the contiguous United States: Oregon, Idaho, Wyoming, Montana, Iowa, Kansas, Nebraska, Missouri, Illinois, Kentucky, Tennessee, Georgia, North Carolina, and South Carolina. It will be first seen from land in the U.S. shortly after 10:15 a.m. PDT (17:15 UTC) at Oregon’s Pacific coast, and then it will progress eastward through Salem, Oregon; Casper, Wyoming; Lincoln, Nebraska; Kansas City, Missouri; St. Louis, Missouri; Hopkinsville, Kentucky; Nashville, Tennessee; Columbia, South Carolina; and finally Charleston, South Carolina.

Map of the solar eclipse of August 21, 2017, showing path of totality.
Map of the solar eclipse of August 21, 2017, showing path of totality.

The longest duration of totality will be 2 minutes 41.6 seconds at about 37°35′0″N 89°7′0″W in Giant City State Park, just south of Carbondale, Illinois, and the greatest extent (width) will be at 36°58′0″N 87°40′18″W near the village of Cerulean, Kentucky, located in between Hopkinsville and Princeton. This will be the first total solar eclipse visible from the Southeastern United States since the solar eclipse of March 7, 1970, which was only visible from Florida.

A partial solar eclipse will be seen from the much broader path of the Moon’s penumbra, including all of North America, northern South America, Western Europe, and some of Africa and north-east of Asia. A partial eclipse will be visible across the width of Canada, ranging from 89% in Victoria, British Columbia to 11% in Resolute, Nunavut. Central America, Mexico, and the Caribbean islands will experience a partial eclipse. In northwestern Europe, the eclipse will only be visible partially, in the evening or at sunset. Only those in Iceland, Ireland, Northern Ireland, Scotland and the Portuguese Azores archipelago will see the eclipse from beginning to end; in the rest of the UK, Norway, the Netherlands, Belgium, France, Spain and Portugal, sunset will occur before the end of the eclipse. In Germany, the beginning of the eclipse will be potentially visible just at sunset only in the extreme northwest of the country. A partial eclipse will be visible only in the Chukchi Peninsula (with about ~40%).

The August 21, 2017, eclipse will be the first with a path of totality crossing the Pacific and Atlantic coasts of the U.S. since 1918. Also, its path of totality makes landfall exclusively within the United States, making it the first such eclipse since the country’s independence in 1776. The path of totality of the eclipse of June 13, 1257, was the last to make landfall exclusively on lands currently part of the United States. The path of this eclipse crosses the path of the upcoming total solar eclipse of April 8, 2024, with the intersection of the two paths being in southern Illinois in Makanda Township at Cedar Lake just south of Carbondale. A small land area, including the cities of Makanda, Carbondale, Cape Girardeau, Missouri, and Paducah, Kentucky, will thus experience two total solar eclipses within a span of less than seven years.

The solar eclipse of August 12, 2045 will have a very similar path of totality over the U.S., about 400 km (250 mi) to the southwest, also crossing the Pacific and Atlantic coasts of the country; however, duration of totality will last over twice as long. An eclipse of comparable length (up to 3 minutes, 8 seconds, with the longest eclipse being 6 minutes and 54 seconds) occurred over the contiguous United States on March 7, 1970, along the southern portions of the Eastern Seaboard, from Florida to Virginia.

Many of my friends and my immediate family live along the band of totality in Kansas and Missouri, Unfortunately, I won’t be able to see any of this eclipse from my home in southern Thailand. There won’t even be a partial eclipse visible from Thailand until September 2, 2035. The next total solar eclipse over the Kingdom will occur on April 11, 2070, long after my bones turn to dust. I suppose my best bet is to visit the U.S. seven years from now if I want to experience such a celestial event in person.

For today’s eclipse, a large number of media outlets have announced plans to broadcast coverage of the event, including television and internet outlets. NASA announced plans to offer streaming coverage through its NASA TV and NASA Edge outlets, using cameras stationed on the ground along the path of totality, along with cameras on high-altitude balloons, jets, and coverage from the International Space Station; NASA stated that “never before will a celestial event be viewed by so many and explored from so many vantage points — from space, from the air, and from the ground.” ABC, CBS, and NBC announced that they would respectively broadcast live television specials to cover the eclipse with correspondents stationed across the path of totality, along with CNN, Fox News Channel, Science, and The Weather Channel. The PBS series Nova will present streaming coverage on Facebook hosted by Miles O’Brien, and air a special episode chronicling the event — “Eclipse Over America” — later in the day (which will mark the fastest production turnaround time in Nova history).

Other institutions and services also announced plans to stream their perspectives of the eclipse, including the Exploratorium in San Francisco, the Elephant Sanctuary of Hohenwald, Slooh, and The Virtual Telescope Project. The Eclipse Ballooning Project, a consortium of schools and colleges that will send 50 high-altitude balloons into the sky during the eclipse to conduct experiments, will provide streams of footage and GPS tracking of its launches.

Many thousands of people are planning to travel to locations along the path of totality. From what I’ve read, you really don’t want to settle for the partial eclipse if you have the opportunity to get someplace to see the full total eclipse. There are expected to be logistical problems with the influx of visitors, especially for smaller communities. Logistically, the demand for portable toilets will be “astronomical,” with municipalities inside and alongside the path of totality planning for the sudden influx of people. Volunteers in smaller towns as with Lathrop, Missouri — which will be coincidentally celebrating the 150th anniversary of its founding — struggled to arrange viewing sites and logistics for what could be either a tourism boom or a disaster.

In the American West, illegal camping is a major concern, including near cities like Jackson Hole, Wyoming. Idaho’s Office of Emergency Management noted that Idaho was a prime viewing state, and advised jurisdictions to prepare for increased loads on their services; nearly every hotel and motel room, campground, and in some cases backyards for nearly 100 miles (160 km) miles north and south of the path of totality had been reserved several months if not years in advance. The state’s population may temporarily increase by a third, with 370,000 to 500,000 visitors projected in state of 1.6 million people.

Oregon Governor Kate Brown authorized the deployment of the National Guard (six aircraft and approximately 150 soldiers), given that the sudden influx of tourists will occur during the peak of that state’s fire season; the soldiers will perforce also be available for fire-fighting duties if needed. Furthermore, given that the expected increase in population of one million will closely mimic the increased demand in emergency services, hospital staffing will be augmented as well as blood supplies and anti-snake bite antidote along the totality line. The emergency room of the hospital of Madras, Oregon (population 6,700), for example, is anticipating a six-fold increase in patients; as the hospital only has 25 beds, medical evacuation is anticipated. The closest precedent for statewide planners is the annual Sturgis motorcycle rally in South Dakota, when approximately half a million people descend on the town.

This past Thursday — August 17 — it was reported that traffic was backed up for fifteen miles on U.S. Highway 26 near Prineville in the state of Oregon, the turnoff to an eclipse festival, as thousands arrived; some gas stations there and in Bend had briefly run out of gasoline the day before.

United States #5211 (2017) first day cover
United States #5211 (2017) first day cover

Scott #5211 was released by the United States Postal Service on June 20, 2017, to commemorate today’s total solar eclipse. It is a single self-adhesive stamp printed in sheets of 16. This is a “Forever” stamp meaning that it will always be equal in value to the current First-Class Mail 1-ounce price, regardless of any future changes in that price. Currently, that value is 49¢. Designed by USPS art director Antonio Alcalá of Alexandria, Virginia, 60 million copies of the Total Solar Eclipse Forever stamp have been offset printed on the Alprinta 74 press by Banknote Corporation of America at Brownsville Summit, North Carolina, on phosphor-tagged paper.

This is the first U.S. stamp to use thermochromic ink which reveals a second image when you rub your thumb or fingers on the eclipse image; the heat imparted to the stamp surface causes an underlying image of the full moon to be revealed. Afterward, the image reverts back to the eclipse as it cools.

The photograph of the total solar eclipse on the stamp was taken at Jalu, Libya on March 29, 2006, by Fred Espenak. The stamp’s alternate image is a photo of the full moon taken by Espenak at his observatory in Portal, Arizona in 2010. Known as “Mr. Eclipse”, Espenak is a retired NASA astrophysicist.

The stamp’s First-Day-of-Issue ceremony took place on June 20, 2017 at the University of Wyoming’s Art Museum in conjunction with its annual summer solstice celebration. That building was designed with an architectural feature whereby, on the day of the summer solstice each year, a single beam of sunlight moves across the floor and shines on a silver dollar embedded in the floor in the center of the Rotunda Gallery at noon.

The U.S. Postal Service notes that exposure to ultraviolet (UV) light causes degradation of thermochromic inks, so the eclipse stamps should be shielded from sunlight to preserve their thermochromic behavior. To help with this, the Postal Service is sending panes of this stamp to purchasers in special UV-blocking envelopes. In addition, UV-protective sleeves for the eclipse stamps are available from post offices for 25¢ each.

United States #5211 (2017) full pane
United States #5211 (2017) full pane

Looking directly at the photosphere of the Sun (the bright disk of the Sun itself), even for just a few seconds, can cause permanent damage to the retina of the eye, because of the intense visible and invisible radiation that the photosphere emits. This damage can result in impairment of vision, up to and including blindness. The retina has no sensitivity to pain, and the effects of retinal damage may not appear for hours, so there is no warning that injury is occurring.

Under normal conditions, the Sun is so bright that it is difficult to stare at it directly. However, during an eclipse, with so much of the Sun covered, it is easier and more tempting to stare at it. Looking at the Sun during an eclipse is as dangerous as looking at it outside an eclipse, except during the brief period of totality, when the Sun’s disk is completely covered (totality occurs only during a total eclipse and only very briefly; it does not occur during a partial or annular eclipse). Viewing the Sun’s disk through any kind of optical aid (binoculars, a telescope, or even an optical camera viewfinder) is extremely hazardous and can cause irreversible eye damage within a fraction of a second.

Viewing the Sun during partial and annular eclipses as well as during total eclipses outside the brief period of totality requires special eye protection, or indirect viewing methods if eye damage is to be avoided. The Sun’s disk can be viewed using appropriate filtration to block the harmful part of the Sun’s radiation. Sunglasses do not make viewing the Sun safe. Only properly designed and certified solar filters should be used for direct viewing of the Sun’s disk.

During the lead-up to the August 21 eclipse, concerns were raised over the sale of glasses that do not properly filter light for safe viewing of the eclipse. The American Astronomical Society and NASA issued guidance and a list of reputable vendors of solar filtering products — whose criteria includes certification of compliance with the international standard ISO 12312-2, and that the user should be able to see very little through the filter except for the Sun itself, sunlight reflected off shiny metal, or similarly-intense light sources such as an LED flashlight.

However, a large number of unsafe filtering glasses began to proliferate on websites such as during the lead-up to the eclipse, including those that claimed to have ISO certification but did not actually undergo testing or had incomplete certification information, and those that were counterfeits of those from vendors the AAS considered reputable such as, in particular, American Paper Optics, which published information detailing the differences between its glasses and counterfeits. On July 27, 2017, Amazon began to require that all eclipse viewing products sold on its website have a submission of origin and safety information, and proof of an accredited ISO certification. In mid-August 2017, Amazon recalled and pulled listings for eclipse viewing glasses that “may not comply with industry standards”, and issued refunds to those that had purchased them.

The safest way to view the Sun’s disk is by indirect projection. This can be done by projecting an image of the disk onto a white piece of paper or card using a pair of binoculars (with one of the lenses covered), a telescope, or another piece of cardboard with a small hole in it (about 1 mm diameter), often called a pinhole camera. The projected image of the Sun can then be safely viewed; this technique can be used to observe sunspots, as well as eclipses. Care must be taken, however, to ensure that no one looks through the projector (telescope, pinhole, etc.) directly.

Viewing the Sun’s disk on a video display screen (provided by a video camera or digital camera) is safe, although the camera itself may be damaged by direct exposure to the Sun. The optical viewfinders provided with some video and digital cameras are not safe. Securely mounting #14 welder’s glass in front of the lens and viewfinder protects the equipment and makes viewing possible. Professional workmanship is essential because of the dire consequences any gaps or detaching mountings will have. In the partial eclipse path, one will not be able to see the corona or nearly complete darkening of the sky, however, depending on how much of the Sun’s disk is obscured, some darkening may be noticeable. If three-quarters or more of the sun is obscured, then an effect can be observed by which the daylight appears to be dim, as if the sky were overcast, yet objects still cast sharp shadows.

Baily's beads during the total solar eclipse seen from Manggar Beach, Balikpapan, East Kalimantan in Indonesia on March 9, 2016
Baily’s beads during the total solar eclipse seen from Manggar Beach, Balikpapan, East Kalimantan in Indonesia on March 9, 2016

As the eclipse approaches totality, the shrinking visible part of the photosphere becomes very small producing Baily’s beads. These are caused by the sunlight still being able to reach the Earth through lunar valleys. Totality then begins with the diamond ring effect, the last bright flash of sunlight.

It is safe to observe the total phase of a solar eclipse directly only when the Sun’s photosphere is completely covered by the Moon, and not before or after totality. During this period, the Sun is too dim to be seen through filters. The Sun’s faint corona will be visible, and the chromosphere, solar prominences, and possibly even a solar flare may be seen. At the end of totality, the same effects will occur in reverse order, and on the opposite side of the Moon.

Photographing an eclipse is possible with fairly common camera equipment. In order for the disk of the Sun/Moon to be easily visible, a fairly high magnification long focus lens is needed (at least 200 mm for a 35 mm camera), and for the disk to fill most of the frame, a longer lens is needed (over 500 mm). As with viewing the Sun directly, looking at it through the optical viewfinder of a camera can produce damage to the retina, so care is recommended. Solar filters are required for digital photography even if an optical viewfinder is not used. Using a camera’s live view feature or an electronic viewfinder is safe for the human eye, but the Sun’s rays will irreparably damage digital image sensors unless the lens is covered by a properly designed solar filter.

United States #5211 (2017) reverse of full pane with map showing path of totality for the August 21, 2017 total solar eclipse
United States #5211 (2017) reverse of full pane with map showing path of totality for the August 21, 2017 total solar eclipse

A total solar eclipse provides a rare opportunity to observe the corona (the outer layer of the Sun’s atmosphere). Normally this is not visible because the photosphere is much brighter than the corona. According to the point reached in the solar cycle, the corona may appear small and symmetric, or large and fuzzy. It is very hard to predict this in advance. Phenomena associated with eclipses include shadow bands (also known as flying shadows), which are similar to shadows on the bottom of a swimming pool. They only occur just prior to and after totality, when a narrow solar crescent acts as an anisotropic light source.

There are numerous resources available giving information about today’s solar eclipse. The website of the Astronomical Society of the Pacific does a great job of listing many of these. NASA has a dedicated eclipse site full of information and will also provide live video streams from across the U.S.  The National Science Teachers Association has created a nice observer’s guide and has state-by-state guides to the prime viewing locations. At this point, you’ve got about twelve hours to get as close to the center-line as possible before it all begins. Here in Thailand, it will be past my bedtime (early class tomorrow), so I’ll probably seek out videos on YouTube.


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