Dr.Sky “Great American Total Solar Eclipse Expedition Survival Guide 2017”

August 21st 2017

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Introduction:

Welcome to our Dr.Sky.com website coverage of what may well be the largest Astronomy
event in the past century!
We hope that this tutorial, will be of help to you and yours, so you may get the most out of
this rare celestial event!
We believe the content below, will help answer many of your questions and concerns.
E-mail the Dr.Sky Team at: drsky@cox.net……
Some History……..

I have had the honor of being able to witness four of these type eclipses…..March 7th 1970,
in Perry, Florida…..July 10th 1972, in far northern Canada in Quebec…..May 30th 1984 ….
a near total eclipse ( deep annular), along costal Maryland……July 11th 1991…a great total
solar eclipse, from the big island in Hawaii……and now…the August 21st 2017, “Great American Total Solar Eclipse”, from Rexburg, Idaho!

The next major total solar eclipse, visible in the USA, will occur on April 8th 2024!

I was lucky, I saw this rare phenomenon, within two years between the first eclipse in 1970,
twelve years between the 1972 eclipse and the 1984 event. After that, there was seven years
between eclipses ….and finally, 26 years between the 2017 eclipse and the 1991 event!
Way too long to wait!

How many eclipses have you seen? And if you did see one, was it a true total solar eclipse?

These type of eclipses are rare, if you stay in the same location and wait for one to return to
your home….after you see your FIRST one, you will have true “Eclipse Fever” and want to
see your next one!

Some say that it takes around 350 years on average for a total solar eclipse to return to the exact location that you saw the last one!

Either way, we hope that this basic, but informative guide will help you to enjoy this rare
celestial event, in comfort and safety!

 

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Here is a rare photo, from our 1972 Eclipse Expedition to Canada. Here is my Dad, Mom and
brother Joe…just 3 years old!

We ran a special eclipse tour to a little town in Quebec, Cap Chat, to see the July 1972 event!
The Hackensack Astronomy Club made the trip and I was just 16 years old!

Watergate was going on…the war in Vietnam , Apollo 16 had landed on the moon and Apollo 17 was to get there in December 1972….a long time ago!
Our Astronomy club, published a magazine called the “ECLIPTIC” and we ran it off on the
old mimeograph machines…what a smell!

We actually had a role for each person in the club, to make the eclipse trip possible!

 

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What Is A Solar Eclipse?

A solar eclipse is a natural event that takes place on Earth when the Moon moves in its orbit between Earth and the Sun (this is also known as an occultation). It happens at New Moon, when the Sun and Moon are in conjunction with each other. If the Moon was only slightly closer to Earth, and orbited in the same plane and its orbit was circular, we would see eclipses each month. The lunar orbit is elliptical and tilted with respect to Earth’s orbit, so we can only see up to 5 eclipses per year. Depending on the geometry of the Sun, Moon and Earth, the Sun can be totally blocked, or it can be partially blocked.

During an eclipse, the Moon’s shadow (which is divided into two parts: the dark umbra and the lighter penumbra) moves across Earth’s surface. Safety note: do NOT ever look at the Sun directly during an eclipse unless it is during a total solar eclipse. The bright light of the Sun can damage your eyes very quickly.

Facts About Solar Eclipses

Depending on the geometry of the Sun, Moon, and Earth, there can be between 2 and 5 solar eclipses each year.
Totality occurs when the Moon completely obscures Sun so only the solar corona is showing.
A total solar eclipse can happen once every 1-2 years. This makes them very rare events.s.

The longest a total solar eclipse can last is 7.5 minutes.

The width of the path of totality is usually about 160 km across and can sweep across an area of Earth’s surface about 10,000 miles long.
Almost identical eclipses occur after 18 years and 11 days. This period of 223 synodic months is called a saros.

During a total solar eclipse, conditions in the path of totality can change quickly. Air temperatures drop and the immediate area becomes dark.
If any planets are in the sky at the time of a total solar eclipse, they can be seen as points of light.

TOTAL SOLAR ECLIPSE

A total solar eclipse occurs when the Moon completely blocks the solar disk. In a total solar eclipse, the narrowest part of the path (where the Sun is completely blocked and the Moon casts its darkest shadow (called the umbra)) is called the “zone of totality”.

Observers in this path see a darkened Sun (often described as a “hole in the sky”) with the ghostly glow of the solar corona extending out to space. A phenomenon called “Bailey’s Beads” often appears as sunlight shines out through valleys on the lunar surface. If the Sun is active, observers can also see solar prominences, loops, and flares during totality. A total solar eclipse is the ONLY time when it is safe to look directly at the Sun. ALL other solar observations (even in partial phases) require special solar filters so that you do not harm your eyes.

Total solar eclipses have not always been visible from Earth. In the past, the Moon was too close to Earth and during eclipses it completely blotted out the Sun’s disk. Over time, the lunar orbit has changed at the rate of just over 2 cm per year and in the current epoch, the alignment is nearly perfect at times. However, the Moon’s orbit will continue to widen, and in perhaps 600 million years, total solar eclipses will no longer occur. Instead, future observers will see partial and annular eclipses only.

ANNULAR SOLAR ECLIPSE

Not every solar eclipse is a total one. When the Moon is farther away in its orbit than usual, it appears too small to completely cover the Sun’s disk. During such an event, a bright ring of sunlight shines around the Moon. This type of eclipse is a called an “annular” eclipse. It comes from the Latin word “annulus” which means “ring”.

The period of annularity during such an eclipse can last anywhere from 5 or 6 minutes to up to 12 minutes. However, even though the Sun is mostly covered by the Moon, enough bright sunlight escapes during annularity that observers cannot ever look at the Sun directly. These events require eye protection throughout the entire eclipse.

PARTIAL SOLAR ECLIPSE

A partial solar eclipse occurs when Earth moves through the lunar penumbra (the lighter part of the Moon’s shadow) as the Moon moves between Earth and the Sun. The Moon does not block the entire solar disk, as seen from Earth. Depending on your location during a partial eclipse, you might see anything from a small sliver of the Sun being blotted out to a nearly total eclipse.

To view any eclipse safely, use approved filters or use an indirect method of viewing, such as projecting sunlight through a telescope and onto a white piece of paper or cardboard. NEVER look at the Sun through a telescope unless it has the appropriate filter. Blindness and severe eye damage can result due to improper observation technique.

 

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Eye Safety and Solar Eclipses-
B. Ralph Chou, MSc, OD
Associate Professor, School of Optometry, University of Waterloo

A total solar eclipse is probably the most spectacular astronomical event that most people will experience in their lives. There is a great deal of interest in watching eclipses, and thousands of astronomers (both amateur and professional) travel around the world to observe and photograph them.
A solar eclipse offers students a unique opportunity to see a natural phenomenon that illustrates the basic principles of mathematics and science that are taught through elementary and secondary school. Indeed, many scientists (including astronomers!) have been inspired to study science as a result of seeing a total solar eclipse. Teachers can use eclipses to show how the laws of motion and the mathematics of orbital motion can predict the occurrence of eclipses. The use of pinhole cameras and telescopes or binoculars to observe an eclipse leads to an understanding of the optics of these devices. The rise and fall of environmental light levels during an eclipse illustrate the principles of radiometry and photometry, while biology classes can observe the associated behavior of plants and animals. It is also an opportunity for children of school age to contribute actively to scientific research – observations of contact timings at different locations along the eclipse path are useful in refining our knowledge of the orbital motions of the Moon and earth, and sketches and photographs of the solar corona can be used to build a three-dimensional picture of the Sun’s extended atmosphere during the eclipse.

However, observing the Sun can be dangerous if you do not take the proper precautions. The solar radiation that reaches the surface of Earth ranges from ultraviolet (UV) radiation at wavelengths longer than 290 nm to radio waves in the meter range. The tissues in the eye transmit a substantial part of the radiation between 380 and 1400 nm to the light-sensitive retina at the back of the eye. While environmental exposure to UV radiation is known to contribute to the accelerated aging of the outer layers of the eye and the development of cataracts, the concern over improper viewing of the Sun during an eclipse is for the development of “eclipse blindness” or retinal burns.

Exposure of the retina to intense visible light causes damage to its light-sensitive rod and cone cells. The light triggers a series of complex chemical reactions within the cells which damages their ability to respond to a visual stimulus, and in extreme cases, can destroy them. The result is a loss of visual function which may be either temporary or permanent, depending on the severity of the damage. When a person looks repeatedly or for a long time at the Sun without proper protection for the eyes, this photochemical retinal damage may be accompanied by a thermal injury – the high level of visible and near-infrared radiation causes heating that literally cooks the exposed tissue. This thermal injury or photocoagulation destroys the rods and cones, creating a small blind area. The danger to vision is significant because photic retinal injuries occur without any feeling of pain (there are no pain receptors in the retina), and the visual effects do not occur for at least several hours after the damage is done [Pitts, 1993].
The only time that the Sun can be viewed safely with the naked eye is during a total eclipse, when the Moon completely covers the disk of the Sun. It is never safe to look at a partial or annular eclipse, or the partial phases of a total solar eclipse, without the proper equipment and techniques. Even when 99% of the Sun’s surface (the photosphere) is obscured during the partial phases of a solar eclipse, the remaining crescent Sun is still intense enough to cause a retinal burn, even though illumination levels are comparable to twilight [Chou, 1981, 1996; Marsh, 1982]. Failure to use proper observing methods may result in permanent eye damage or severe visual loss. This can have important adverse effects on career choices and earning potential, since it has been shown that most individuals who sustain eclipse-related eye injuries are children and young adults [Penner and McNair, 1966; Chou and Krailo, 1981].

The same techniques for observing the Sun outside of eclipses are used to view and photograph annular solar eclipses and the partly eclipsed Sun [Sherrod, 1981; Pasachoff & Menzel 1992; Pasachoff & Covington, 1993; Reynolds & Sweetsir, 1995]. The safest and most inexpensive method is by projection. A pinhole or small opening is used to form an image of the Sun on a screen placed about a meter behind the opening. Multiple openings in perfboard, in a loosely woven straw hat, or even between interlaced fingers can be used to cast a pattern of solar images on a screen. A similar effect is seen on the ground below a broad-leafed tree: the many “pinholes” formed by overlapping leaves creates hundreds of crescent-shaped images.

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. All of these methods can be used to provide a safe view of the partial phases of an eclipse to a group of observers, but care must be taken to ensure that no one looks through the device. The main advantage of the projection methods is that nobody is looking directly at the Sun. The disadvantage of the pinhole method is that the screen must be placed at least a meter behind the opening to get a solar image that is large enough to see easily.

The Sun can only be viewed directly when filters specially designed to protect the eyes are used. Most such filters have a thin layer of chromium alloy or aluminum deposited on their surfaces that attenuates both visible and near-infrared radiation. A safe solar filter should transmit less than 0.003% (density~4.5)[1] of visible light (380 to 780 nm) and no more than 0.5% (density~2.3) of the near-infrared radiation (780 to 1400 nm). Figure 24 shows the spectral response for a selection of safe solar filters.

One of the most widely available filters for safe solar viewing is shade number 14 welder’s glass, which can be obtained from welding supply outlets. A popular inexpensive alternative is aluminized mylar manufactured specifically for solar observation. (“Space blankets” and aluminized mylar used in gardening are not suitable for this purpose!) Unlike the welding glass, mylar can be cut to fit any viewing device, and doesn’t break when dropped. Many experienced solar observers use one or two layers of black-and-white film that has been fully exposed to light and developed to maximum density. The metallic silver contained in the film emulsion is the protective filter. Some of the newer black and white films use dyes instead of silver and these are unsafe. Black-and-white negatives with images on it (e.g., medical x-rays) are also not suitable. More recently, solar observers have used floppy disks and compact disks (both CDs and CD-ROMs) as protective filters by covering the central openings and looking through the disk media. However, the optical quality of the solar image formed by a floppy disk or CD is relatively poor compared to mylar or welder’s glass. Some CDs are made with very thin aluminum coatings which are not safe – if you can see through the CD in normal room lighting, don’t use it!! No filter should be used with an optical device (e.g. binoculars, telescope, camera) unless it has been specifically designed for that purpose and is mounted at the front end (i.e., end towards the Sun). Some sources of solar filters are listed in the following section.

Unsafe filters include all color film, black-and-white film that contains no silver, photographic negatives with images on them (x-rays and snapshots), smoked glass, sunglasses (single or multiple pairs), photographic neutral density filters and polarizing filters. Most of these transmit high levels of invisible infrared radiation which can cause a thermal retinal burn (see Figure 24). 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. Solar filters designed to thread into eyepieces that are often provided with inexpensive telescopes are also unsafe. These glass filters can crack unexpectedly from overheating when the telescope is pointed at the Sun, and retinal damage can occur faster than the observer can move the eye from the eyepiece. Avoid unnecessary risks. Your local planetarium, science center, or amateur astronomy club can provide additional information on how to observe the eclipse safely.

There has been concern expressed about the possibility that UVA radiation (wavelengths between 315 and 380 nm) in sunlight may also adversely affect the retina [Del Priore, 1991]. While there is some experimental evidence for this, it only applies to the special case of aphakia, where the natural lens of the eye has been removed because of cataract or injury, and no UV-blocking spectacle, contact or intraocular lens has been fitted. In an intact normal human eye, UVA radiation does not reach the retina because it is absorbed by the crystalline lens. In aphakia, normal environmental exposure to solar UV radiation may indeed cause chronic retinal damage. However, the solar filter materials discussed in this article attenuate solar UV radiation to a level well below the minimum permissible occupational exposure for UVA (ACGIH, 1994), so an aphakic observer is at no additional risk of retinal damage when looking at the Sun through a proper solar filter.

In the days and weeks preceding a solar eclipse, there are often news stories and announcements in the media, warning about the dangers of looking at the eclipse. Unfortunately, despite the good intentions behind these messages, they frequently contain misinformation, and may be designed to scare people from seeing the eclipse at all. However, this tactic may backfire, particularly when the messages are intended for students. A student who heeds warnings from teachers and other authorities not to view the eclipse because of the danger to vision, and learns later that other students did see it safely, may feel cheated out of the experience. Having now learned that the authority figure was wrong on one occasion, how is this student going to react when other health-related advice about drugs, alcohol, AIDS, or smoking is given [Pasachoff, 1997] Misinformation may be just as bad, if not worse than no information at all.

In spite of these precautions, the total phase (and only the total phase) of an eclipse can and should be viewed without filters. It is crucial that you know when to take off and put back on your glasses; see Eye safety during a total solar eclipse

Eclipses In History- From Time and Date.com

Scientific Discoveries
The British astronomer and mathematician, Sir Arthur Eddington, used the total solar eclipse of May 29, 1919 to test Albert Einstein’s theory of general relativity.

By taking pictures of stars near the Sun during totality, Eddington was able to show that gravity can bend light. This phenomenon is called gravitational deflection.

All eclipses worldwide 1900–2099
Helium Named After the Sun
A solar eclipse is also responsible for the discovery of helium. The first piece of evidence for the existence of the second lightest and the second most abundant element known to humans was discovered by the French astronomer Jules Janssen during a total solar eclipse on August 16, 1868. Because of this, it’s named after the Greek word for the Sun: Helios.
Predicting the Emperor’s Future

Surviving records have shown that the Babylonians and the ancient Chinese were able to predict solar eclipses as early as 2500 BCE.
In China, solar eclipses were thought to be associated with the health and success of the emperor, and failing to predict one meant putting him in danger. Legend has it that 2 astrologers, Hsi and Ho, were executed for failing to predict a solar eclipse. Historians and astronomers believe that the eclipse that they failed to forecast occurred on October 22, 2134 BCE, which would make it the oldest solar eclipse ever recorded in human history.

Mythology of eclipses

Substitute Kings
Clay tablets found at ancient archaeological sites show that the Babylonians not only recorded eclipses—the earliest known Babylonian record is of the eclipse that took place on May 3, 1375 BCE—but were also fairly accurate in predicting them. They were the first people to use the saros cycle to predict eclipses. The saros cycle relates to the lunar cycle and is about 6,585.3 days (18 years, 11 days, and 8 hours) long.

How often do solar eclipses occur?

Like the ancient Chinese, the Babylonians believed that solar eclipses were bad omens for kings and rulers. Predicting solar eclipses enabled them to seat substitute kings during solar eclipses with the hope that these temporary kings would face the anger of the Gods, instead of the real king.

Eclipses as Peacemakers

According to the Greek historian Herodotus, a solar eclipse in 585 BCE stopped the war between the Lydians and the Medes, who saw the dark skies as a sign to make peace with each other.

The Greek astronomer Hipparchus used a solar eclipse to determine that the Moon was about 429,000 km (268,000 mi) away from the Earth. This is only about 11% more than what today’s scientists accept as the average distance between the Moon and the Earth.

Kepler Close, Halley Closer

Although early eclipse pioneers, including Chinese astronomer Liu Hsiang, Greek philosopher Plutarch, and Byzantine historian Leo Diaconus tried to describe and explain solar eclipses and their features, it was not until 1605 that astronomer Johannes Kepler gave a scientific description of a total solar eclipse.

More than a century later, Edmund Halley, who the famous Halley’s comet is named after, predicted the timing and path of the total solar eclipse on May 3, 1715. His calculations were only 4 minutes and about 30 km (18 mi) off from the actual timing and path of the eclipse.
Halley’s comet causes 2 annual meteor showers: the Eta Aquarids and the Orionids.

Some Other Notable Solar Eclipses in History

The scientific fascination with solar eclipses has led to some important scientific discoveries about the nature of the Sun, Moon, and our solar system.
Year
Date
Type
Importance
632
January 27
Annular

Visible in Medina, Saudi Arabia, the eclipse coincided with the death of Prophet Mohammad’s son Ibrahim. The Prophet reportedly dismissed rumors that this was a miracle, stating that the Sun and the Moon are signs of God and that they are not eclipsed for the birth or death of any man.
1133
August 2
Total

King Henry’s Eclipse: King Henry I died shortly after the eclipse, prompting the spread of the superstition that eclipses are bad omens for rulers.
1836
May 15
Annular

English astronomer Francis Baily first discovered and described Baily’s beads—a phenomenon that occurs in the seconds before and after totality in a total solar eclipse and annularity in an annular solar eclipse.
1851
July 28
Total

The first photograph of the Sun’s corona was taken by a Prussian photographer called Berkowski.
2009
July 21/22
Total

Longest total solar eclipse of the 21st century. Totality lasted for 6 mins and 39 secs.

Links To Eclipses in History:

cs.astronomy.com/asy/b/astronomy/archive/2014/09/24/the-10-most-important-eclipses-in-history.aspx

www.eclipsewise.com/extra/SEhistory.html

www.bibalex.org/eclipse2006/HistoricalObservationsofSolarEclipses.htm

How Eclipses Are Predicted:

www.webassign.net/seedfoundatCH03-4.ions/ebook/html

astronomy.stackexchange.com/questions/231/what-is-the-formula-to-predict-lunar-and-solar-eclipses-accurately

eclipse.gsfc.nasa.gov/SEmono/reference/explain.html

Your Guide To The 2017 “Great American Solar Eclipse”-

How To Photograph A Solar Eclipse:

www.eclipse2017.org/201grap7/photohing.HTM

www.mreclipse.com/SEphoto/SEphoto.html

The Reaction of Nature /During a Total Solar Eclipse:

Amazing things happen from the natural world, during a total solar eclipse…Here are some
links to what may occur!

americaneclipseusa.com/about-eclipses/total-solar-eclipse-phenomena/

The Amazing “Shadow Bands”/ What Are They? / How To Observe Them!:

eclipse2017.nasa.gov/what-are-shadow-bands

www.strickling.net/shadowbands.htm

Here is an activity that you can participate in, if you are in the path of totality!
How dark will the sky get during the eclipse?:

www.globeatnight.org/eclipse-2017/GaN2017_ActivityGuide_UrsaMajor.pdf

What Will The Sky Look Like At The Moment Of Totality:

Courtesy: Shadow and Sunstance.com

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During the few minutes of totality; Venus and Mercury will be visible in a clear sky, as well as many of the bright stars in the sky.
The Sun will be very close to the bright star, Regulus in Leo the Lion.

How many stars can you see and for how long?

Here is a listing of what we feel are some of the best links for the August 2017 eclipse!

Links:

DR. SKY/ The Dr.Sky Show

www.drsky.com

ECLIPSE LINKS:

www.eclipse2017.org/2017/path_through_the_US.htm

www.greatamericaneclipse.com/

eclipse.gsfc.nasa.gov/eclipse.html

www.greatamericaneclipse.com/statistics/

HOW TO PHOTOGRAPH THE ECLIPSE

www.nikonusa.com/en/learn-and-explore/a/tips-and-techniques/how-to-photograph-a-solar-eclipse.html

www.mreclipse.com/SEphoto/SEphoto.html

COAST TO COAST AM-
Dr.Sky Appears Each Monday Night 10 PM PDT

www.coasttocoastam.com/

The Next Major Eclipse In America- April 8th 2024

xjubier.free.fr/en/site_pages/solar_eclipses/TSE_2024_GoogleMapFull.html

KTAR/ News  92.3 FM/ Dr.Sky Blog:

ktar.com/category/dr-sky-blog/

Amazing Links:

Follow the August 21st 2017 Eclipse / Interactive GOOGLE Map:

xjubier.free.fr/en/site_pages/solar_eclipses/TSE_2017_GoogleMapFull.html

This is the BEST site to look at the details of the eclipse…locations, times, percentage
of eclipse, etc. We suggest you use this and tell others!

Shadow and Substance:

A great site that shows you what you can expect with the eclipse in each state and some great
Eclipse and other sky simulations…..We really like this one and you will too!!!

shadowandsubstance.com/2017/2017e.html