Viewing the Total Solar Eclipse
Entry posted by tbutler ·
It is now three days until the eclipse. In fact as I write this, in 72 hours it will be over. You either get to see it or you don't. The partial eclipse will be visible in all 50 United States and Canada. All of Mexico and Greenland will see the eclipse as a partial eclipse. Even the countries in Central America and the northern half of South America will see a partial eclipse. Western Africa, Spain, Great Britain and Iceland will see a partial eclipse. Even eastern Russia will see a partial eclipse. The only people who will see a total eclipse of the Sun are in that narrow ribbon that stretches across the US from Oregon through Idaho, Wyoming, Nebraska, a teeny tiny corner of Kansas, Missouri, Kentucky, Tennessee, a tiny corner of Georgia, the western tip of North Carolina, and South Carolina. For the rest of the world it is a partial eclipse or no eclipse at all.
As the eclipse begins, everyone will see a partial eclipse as the Moon takes the first tiny bite out of the Sun. It will take about an hour for the Moon to move to a position where it can cover the entire Sun. That will be the total eclipse, the Moon completely hiding the Sun. People on the west coast of the US will see that happen at about 11:17 a.m. Pacific Daylight Time. Twenty minutes later, people in western Wyoming will see this happen at about 11:37 a.m. Mountain Daylight Time. Twenty three minutes later totality occurs at about 1:00 p.m. Central Daylight Time as the shadow of the Moon sweeps past Grand Island in central Nebraska. Twenty minutes after that, the shadow sweeps over western Kentucky at 1:20 p.m. Central Daylight Time. Twenty seven minutes later the shadow sweeps off the Atlantic coast of South Carolina at 2:47 p.m. Eastern Daylight Time. Just ninety minutes from from the Pacific Ocean to the Atlantic Ocean. After the total eclipse exits the east coast of the US, there will be another hour or so of partial eclipse as the Moon slowly uncovers the Sun.
The pattern for those in the ribbon of totality is eclipse starts - partial eclipse - total eclipse - partial eclipse - eclipse ends. The whole process will take about two hours, depending on where you are it can be a little shorter or a little longer. How long will totality last? Just two minutes for those on the west coast of Oregon. By the time the shadow reaches Wyoming the Moon will cover the Moon for almost two minutes and 30 seconds. On the coast of South Carolina the Moon will cover the Sun for two minutes and 34 seconds. In western Kentucky totality will last just over 2 minutes and 41 seconds.
Do you have your eclipse glasses? Are they safe? There are certifications on your glasses. Mine don't have the ones publicized on the Weather Channel but they were recommended by NASA so they are good. Don't know? There are other alternatives. A #14 welding glass will work for viewing the Sun. If you can see anything through your glasses, they are not good solar glasses. You can use your solar glasses to view the Sun right now. Simply go outside, put the glasses on and look up at the Sun. What will you see? You should see a slightly bluish disk that is the Sun. You may be expecting something really big but it won't be giant in size. We think of the Sun as being very large and it is, 109 times the diameter of Earth. Think of a necklace. Now imagine a necklace with beads made of Earth size beads. There would be 109 Earths on that necklace and it would stretch not around the Sun but straight through the center. If the Sun was a fishbowl one million three hundred thousand Earth's could fit into that fishbowl. When you use your eclipse glasses you will be looking at a disk that appears to be about as large as our Moon. In fact it will appear exactly as large as our Moon which is why our Moon can just cover up the Sun.
If you don't have solar glasses you can still watch the eclipse using a small mirror like a compact mirror. A mirror two or three inches in diameter works just fine. The mirror can be square or rectangular and will work very well, just as good as a circular mirror. Hold the mirror in direct sunlight and reflect the sunlight onto the side of a building or an RV. A white or light colored vehicle or building will work best. If you stand close to the building the image will be bright but small. If you stand further back, the image will be larger but not as bright. The geometry of t, his is that the light should be shining on the mirror and the reflection should be falling on the shaded side of a building or RV. At a distance of 100 feet you should have an image about 4 feet in diameter. If you get tired of holding the mirror, tape it to a tripod, a fence post or other support. Don't look into the mirror, that is just like looking directly at the Sun. Using this technique, you may even be able to see sunspots if there are large ones on the Sun's visible light surface.
The method everyone knows is to use a pinhole to project an image of the Sun. In the example above, the mirror is doing the same thing as a pinhole but on a larger scale. Big pinhole, big image. A big pinhole will yield a blurry image. The mirror method will yield a slightly blurry image but this is not noticeable when viewed from twenty feet away. With a true pinhole viewer, you will get a tiny image of the Sun. You can make it longer by making the box you are using longer. The typical diagram shows something like a shoebox. The image will be about 1/8 inch in diameter. Lengthen this to a longer cardboard box and you get a larger image. A sheet of white paper where the image falls will make the image appear brighter. If you can find a refrigerator box, you can carry this to an extreme. Cut a small hole in the box so people can insert their head into the box. This will keep the box dark. Put paper on the opposite end from the pinhole where the image will fall. Cut a one inch hole where the pinhole will go. Cover that hole with a piece of aluminum foil. Use a pin to puncture the aluminum foil to get a nice pinhole. If the box is really dark inside, you will have a nice size image that be seen. If not bright enough, make the hole slightly larger using a pencil point or other similar size object. The pinhole is toward the Sun. Turn the box so that the light coming through the pinhole falls on the paper at the other end of the box. Turn the box so the paper is completely shaded from direct sunlight. There should be a small dot on the white paper. That is an image of the Sun.
A natural variation of the pinhole projector occurs when sunlight filters through the leaves of a tree. Look in the shadow of a tree and you may notice that the spots of sunlight coming through the tree take on a crescent shape as the eclipse proceeds. These are images of the Sun. Sometimes with trees you will see hundreds of images, some overlapping. This works best where the shade is falling on a flat smooth surface like a sidewalk, a parking lot or a porch or deck surface.
The third method is much less desirable in my judgment but it does offer a guarantee of seeing the total eclipse no matter where you live. If you are unable to see the total eclipse in person, this represents the next best thing. You will be able to watch the eclipse and hear it described for you in some cases. The Weather Channel will cover the eclipse from beginning to end from a variety of places along the line of totality. Local TV stations are likely places to get live coverage of the eclipse. The internet will no doubt have many images and perhaps some live coverage as well. You can also look at images of total eclipses by searching the internet. You can see pictures from long ago and from many locations on the Earth. There will be no comparison to the excitement and the drama of standing in the Moon’s shadow and watching the actual eclipse. It would be like going to the library and looking at a book of birds and then claiming that you had a “Big Year.” Setting a record for the number of birds seen in a year. Shoot, why not go for a “Big Day” and see all the birds in the world in one day? I have no doubt that given the resources of the internet, it could be done. This is why I’ve encouraged those who can to get to the path of the total eclipse. It will never get easier or less expensive than when it comes to us here in the US.
Now, for those who are going to see the total eclipse some special instructions. These apply only to those who are within the ribbon of totality described above. Once the Moon completely covers the Sun you can remove your glasses and look directly at the dark "hole in the sky." My first impression of my first total eclipse was that someone had pulled a cork out of the sky leaving a deep dark hole where the Sun used to be, an intense dark spot where the Sun used to be. Around it will be the corona of the Sun. The corona is the outer atmosphere of the Sun. It is safe to view the corona without viewing glasses or other eye protection. The corona may be a uniform circular veil around the eclipsed Sun, fading with distance until it is no longer visible. Depending on solar activity, sunspots and solar prominences the corona may be quite irregular with spikes and gaps. I’ve already described in a previous post the planets Venus to the west of the Sun and Jupiter to the east of the Sun which will be visible during totality. For those with a partial eclipse you can look for these planets by blocking out the sun near its maximum and looking to the west and east of the Sun for Venus and Jupiter. Those viewing the total eclipse will get the bonus of seeing a number of other bright stars in the sky. Orion’s bright stars, Rigel and Betelgeuse, Sirius, the dog star and Pollux and Castor in Gemini may all be visible to the west of the Sun. East of the Sun you may see Spica in the constellation Virgo, Antares in the constellation Scorpius, Vega in Lyra will all be to the east of the Sun.
Here are a few of the things you may notice during the eclipse. In the beginning, the changes will be slight and if you are far from the center line of the eclipse you may not notice much at all. As the eclipse deepens, the nature of the light will change, shadows will become less sharp, the bright light fades and the shadow seems less dark. The temperature will drop, birds will sing like they do in the morning and evening before going to roost. Some birds will go to roost in areas where the eclipse is near total or total. The wind speed may drop and possibly become calm. The reverse will happen as totality ends and the Sun returns to the sky.
As the totality begins and again at the end you may see Baileys Beads as sunlight dances through the valleys between mountains on the Moon. The first direct glimmer of sunlight as the Moon covers or uncovers the Sun is called the diamond ring. It will be a fleeting moment, it signals that you must look away and put your glasses back on. Take a breath and reflect on two of the most amazing minutes of your life. You have stood in the shadow of the Moon and seen the Sun like few other people have. To ancient people it had various meanings, often described as fear and dread. It was frequently thought of as an evil omen. Ancient people feared the Sun might never return. Now, we understand what is happening. We can enjoy the eclipse as a unique and rare natural occurrence.
Such are the benefits of the age of enlightenment.
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