Stargazing U.S. Solar Eclipse of Aug. 21, 2017

[tony873004]

I was in Hawaii in 1991, and Shanghai in 2009. Both times it rained during totality. In Hawaii, there were patches of clear sky, but just not where the Sun was. I don't remember seeing any stars or planets. The sky was not pitch black. It was like the same brightness as 25 minutes after sunset. If I had to walk back to my car during totality, I would not have needed a flashlight. It's possible that all the clouds in the vicinity that were not experiencing totality let a lot of light bleed in.

In Shanghai, the sky was completely clouded over. It got dark like midnight, but the clouds may have had a lot to do with that. In both cases, I was near centerline, and the eclipse path was very wide, producing about 6 minutes of totality.

My guess is that for the darkest eclipse, you want to be in an area that is cloud-free for a few hundred kilometers, a wide eclipse path, and close to the centerline.

The August eclipse will not have a wide path. Even at mid-eclipse on the centerline, you will be only 30 miles away from areas not experiencing totality. Any clouds in those areas will be visible to you and reflecting direct sunlight.

In 2012 I was near Redding, CA for an annular eclipse. The sky was cloud-free. The Moon was rather small compared to the Sun. At the height of annularity, the sky darkened to about the level of perhaps 1 minute before sunset. I had no trouble spotting Venus. I wasn't even looking for it. It just stood out.

I've read that it takes up to 30 minutes for your eyes to fully dark-adapt. A few years ago, I was a volunteer at my University's planetarium, and experimented with this. I found about 10 minutes was all it took. Maybe they got a little more sensitive over the next 20 minutes, but I didn't notice it. I also noticed that it takes a few minutes for your eyes to un-adapt. For example, with dark-adapted eyes, I stepped out into the hall for a minute. The late-afternoon sun made the hall very bright. But when I returned to the darkened planetarium, my eyes were still dark adapted.

For August's eclipse, I'll probably wear dark sunglasses (maybe even 2 pairs!) during the partial phase, and have a handheld solar filter. As totality approaches, I'll try to get as dark-adapted as possible. It's tempting to look up at the partial phases. There's the Moon creeping across the Sun. How cool is that! But remember, after totality, it will repeat the partial phases for you. In the 2012 Annular eclipse, everyone was watching the partial phases leading up to annularity, then when annularity ended, they all got in their cars and left. Of the 100+ people at my observing location, there were only a handful of us who stayed to watch the waning partial phases.

I'm not going to participate in the activity of trying to spot constellations. Totality lasts only 2 minutes. This is the only opportunity I have to see the corona. I'll probably use unfiltered binoculars for a better view. I may take a quick glance just to gauge the darkness of the sky, but if I want to look at constellations, I can do that any night!

I may set up a 360 degree video camera and just let it run. I don't want to be playing with camera equipment during totality. No matter how nice my photos may turn out, lots of people with better equipment are going to get much better pictures, and they'll be posted all over the internet the next day.

The brightness in my simulation is just a guess based on having seen 3 annular eclipses, many partial eclipses, and 2 total (but raining) eclipses. I was aiming for what a user may perceive. For example, when the Moon is half covering the Sun, I imagine a light meter would tell me that my surroundings were half as bright. But the human eye doesn't see that. Your eyes sense brightness approximately logarithmically and your pupils dilate making it hard to tell the difference. Until the Sun is about 90% covered, an unsuspecting person won't notice anything unusual. So in my simulation, there's not much difference in the sky brightness with the Sun half covered. In my simulation, even after totality begins, the sky continues to darken until mid-eclipse. I'm guessing that deeper in the umbra is darker, as I am farther away from areas that are outside totality.

 

[Janus]

[5] @tony873004 , is the brightness in your gif just a guesstimation, or is there science behind that? Some of my friends are like; "Whateva... I'm stayin' home. It'll be 98% covered from my front porch. What's the deal with totality?"

Almost total compared to total. (images taken from screen shots of Worldwide Telescope)

[6] Where the hell will the Milky Way be? To my knowledge, I've never seen the Milky way. I know the center is in Sagittarius, wherever the hell that constellation is.

At the time of eclipse, about 48 degrees to the South, rising upwards towards the South. It takes a clear night well away from light pollution to see it well.

[7] Where is Sagittarius?

Below the horizon during the eclipe

ppps. Just as an FYI, I can recognize about 5 constellations: Big & Little Dipper, Cassiopeia, Orion, and Taurus. Everything else, is just a bunch of stars.

There's a really neat app for your smart phone that can help with that. Just point your phone at the region of the sky that you are interested in and it will show you a labeled map of that part of the sky. (it will even include planets). It is called SkyMap.

 

[OmCheeto]

This is why I love PF.
Ask for a gram of information, and get a kilogram.

Easier to see during the night. But you'll have to get away from big cities to see it nicely.

Well then, it's a good thing I'll be on station for at least 3 days.
A Google Earth kmz supplied by some very kind people in Germany has yielded me this map:

Red dots, yellow squiggly line, and green ellipse are all actually in the all black zone.

There's a really neat app for your smart phone

I still don't have a smart phone.
But I googled the bejeezitz out of this, and came up with:

The yellow bullseye looking thing is the galactic center. I mac-doodle-painted in the "galactic plane"ish stuff.
I've seen hundreds of images, but am curious what it looks like in real life.

For August's eclipse, I'll probably wear dark sunglasses (maybe even 2 pairs!) during the partial phase, and have a handheld solar filter. As totality approaches, I'll try to get as dark-adapted as possible. It's tempting to look up at the partial phases. There's the Moon creeping across the Sun. How cool is that! But remember, after totality, it will repeat the partial phases for you. In the 2012 Annular eclipse, everyone was watching the partial phases leading up to annularity, then when annularity ended, they all got in their cars and left. Of the 100+ people at my observing location, there were only a handful of us who stayed to watch the waning partial phases.

Bazinga! According to what everyone has posted so far, you've been to the most eclipses(5), and I must say, have had the best suggestions so far.
I would have never thought to have looked at the partial AFTER the eclipse.

I was out yesterday, following your instructions from your April 11, 2017 post;

"In a few days from now (~April 17-20), the azimuth of sunrise will be the same as on eclipse day, August 21.
If you happen to live in the zone to totality, this may serve as a good preview of the Sun's position and motion on eclipse day"​

and noted that the sun is so high in the sky, that my camera movement is encumbered by the geometry of my tripod.

And your April 14, 2016 post;

"With the Sun taking up 50% of the picture, you will be losing the outer edges of the corona. ... Since the Moon has the same angular size as the Sun, take a picture of the Moon with your 300mm lens."​

Apparently, 36x zoom is too much. My image from yesterday:

I'm not going to participate in the activity of trying to spot constellations.

The experiment doesn't even make sense to me. How the hell do you calibrate millions of eyes? That's why I'm taking my solar panel, and collecting voltage data.
I know @nsaspook has some fancy stuff that does that automatically. Perhaps I can talk him into doing the experiment.

ps. Ehr mehr gerd. I am so not ready for this. But much readier than I was before.
Thanks everyone!

 

[tony873004]

Look at the pictures on Miloslav Druckmüller's site.
http://www.zam.fme.vutbr.cz/~druck/Eclipse/Ecl2016i/0-info.htm
This will give you a very good idea as to how to frame your image. His images are created from bracketed images, so you get a dynamic range closer to what the human eye sees.

I just found the video file from my Shanghai trip, and converted it into a Youtube. This was taken by Lancelot Kao, the chairman of the Astronomy Department at City College of San Francisco. I was lucky enough to have met up with him and others in the CCSF Astronomy Department while I was in Shanghai. You can see me a few times in this video. I'm one of the only people NOT holding an umbrella. It was 90 degrees F (~30 C). Being wet felt good, and umbrellas blocked the view.

This video begins about 2.5 minutes before totality begins.

 

[Janus]

This is why I love PF.

I've seen hundreds of images, but am curious what it looks like in real life.

The best view of the Milky Way I ever saw came quite by accident. A friend and I were driving up the Oregon coast late one winter night, and he had to pull off at some lonely point of US 101 to do some quick car maintenance. I got out to stretch my legs, looked up, and it was just blazing across the sky.

 

[OmCheeto]

The sky was not pitch black. It was like the same brightness as 25 minutes after sunset. If I had to walk back to my car during totality, I would not have needed a flashlight. It's possible that all the clouds in the vicinity that were not experiencing totality let a lot of light bleed in.

I just found this 360° video. It looks exactly as you've described it.

Published on Apr 30, 2016
Experience the Total Solar Eclipse that took place across Indonesia on the March 9, 2016.
We traveled to see it first hand and it was incredible.

Listen to the cheer of the crowd and then the breath of silence it brings. It takes people's breathe away.

Words cannot describe the feeling of a total eclipse. It's as if someone pulled a curtain in front of the sun during the day. Everyone should make it a mission to witness a total eclipse.

Totality began at 8:37:47 am and ended at 8:39:52 am​

I also found an informational video.



Probably good for people that don't know anything about eclipses.
I of course watched it from start to finish.

2 interesting facts mentioned:

6:50 "Even if 99% of the solar disc is blocked, the remaining 1% is still 4,000 times brighter than a full moon."
9:40 "Thin, wavy lines of shadows known as shadow bands will appear on the ground, and scientists to this day, do not yet fully understand how they are created."​

Shadow bands? What sorcery is this?

https://eclipse2017.nasa.gov/what-are-shadow-bands-0 [NASA]

These are among the most ephemeral phenomena that observers see during the few minutes before a total solar eclipse. They appear as a multitude of faint bands that can be seen by placing a white sheet of paper several feet square on the ground.They look like ripples of sunshine at the bottom of a pool, and their visibility varies from eclipse to eclipse. 19th century observers interpreted them as interference fringes caused by some kind of diffraction phenomenon. The Sun, however, is hardly a 'point source' and the patterns are more random than you might expect from diffraction effects.

The simplist explanation is that they arise from atmospheric turbulence. When light rays pass through eddies in the atmosphere, they get refracted. Unresolved distant sources simply 'twinkle', but for nearby large objects, the incoming light can get split into interfering bundles that recombine on the ground to give mottled patterns of light and dark bands, or portions of bands. Near totality, the image of the sun is only a thin crescent a few arc seconds wide, which is about the same size as the atmospheric eddies as seen from the ground. Bands are produced because the sun's image is longer in one direction than another. The bands move, not at the rate you would expect for the eclipse but at a speed determined by the motion of the atmospheric eddies.​

Thanks, NASA!

hmmmm... I didn't realize they were so into this. https://eclipse2017.nasa.gov/

And how cool is this? Citizen Science!
Too many projects to list.
I'll have to find one that I can contribute to.

This one looks like something I was planning on doing:

GLOBE at night (NOAO) (link is external) – This is an international citizen-science campaign to raise public awareness of the impact of light pollution by inviting citizen-scientists to measure and submit their night sky brightness observations. In 2015, citizen scientists from around the world contributed 8,337 data points. Whether you use a smartphone, tablet or computer, you can submit your data in real time with the GLOBE at Night web app - now available in 28 languages! ​

I may have to finally invest in a smartphone...
Emphasis on "may"...

--------------

I also finally ordered some new equipment.

RAINBOW SYMPHONY STORE
Thank you Om!
$27.67
Solar Viewing Film - Our Black Polymer Solar Filter Film provides a pleasing natural light orange image of the sun.
2 mil Optical Grade polymer for use on Telescopes, Finder Scopes, Binoculars and Cameras.
12" x 12" Sheets - Meets the Standard for ISO 12312-2:2015

https://www.iso.org/standard/59289.html
ISO 12312-2:2015 applies to all afocal (plano power) products intended for direct observation of the sun, such as solar eclipse viewing.​

I decided that with a 12x12" sheet, I could make my own glasses, camera lens and binocular covers. And maybe have some left over, in case I ever buy a telescope, and want to look at sunspots, or whatever.

 

[tony873004]

I just found this 360° video. It looks exactly as you've described it.

I saw that video too. I've got a Samsung VR headgear for my Galaxy phone. That video looks awesome when it surrounds you. I may decide to drop $250 on a 360 camera so I can make one too. That's the only type of photography I want to do: something where I can turn on a camera a few minutes before totality begins, and turn it off a few minutes after. I don't want to be adjusting a tripod minute-by-minute and messing with exposure time during totality. Hopefully I can capture the approaching and receeding shadow.

In the Indonesia 360 video, I think it got darker than that. The camera's auto-iris probably kicked in taking advantage of the camera's low-light capability and making the scene appear brighter than a human eye would perceive. If I try that, I'll have to find a way to turn that off.

12" x 12" Sheets

I got 2 of these a few months ago. I already made some binocular filters. On a 3-d printer, I recreated the lens caps and put holes in them to accept the film.
I'm going to use the rest to make a bunch of hand-held cardstock filters.

Shadow bands? What sorcery is this?

I once lived in a house where you could see these every day. A few minutes after sunrise, the sun was still behind a hill about 1 mile away. When it finally peeked above the hill, the light was very wavy for a few seconds as bands of shadow raced across the front stairs.

 

[OmCheeto]

I once lived in a house where you could see these every day. A few minutes after sunrise, the sun was still behind a hill about 1 mile away. When it finally peeked above the hill, the light was very wavy for a few seconds as bands of shadow raced across the front stairs.

Interesting. I'd never even heard of them until yesterday. I also see this is the first time they've been mentioned here at PF.
I watched a few videos, and they are apparently so subtle, that it's difficult for video cameras to capture them.
And I haven't seen any mention of them except in the context of eclipses. (Though, I only searched for a few minutes.)

I find the wiki entry on them somewhat hilarious.

wiki on Shadow Bands;

"In 2008, Dr. Stuart Eves suggested that shadow bands might be caused by infrasound"

Professor Brian Jones stated, "The [accepted] theory works; there's no need to seek an alternative."​

The guy in the video I posted yesterday said scientists don't fully understand them.
But I like NASA's explanation. It seems very reasonable.

 

[OmCheeto]

Whoop! Whoop!

Solar filter arrived yesterday.

Test #1:

72x zoom.

Have not a clue why i-Photo thinks that's a face.

 

[OmCheeto]

I'm really glad I bought the 12x12 inch sheet now.

The sun is REALLY tiny to the naked eye, when you look at it through ISO approved filter media.
Even looking at it with 7x35 binoculars, it seemed kind of tiny. Though, more jiggly than tiny.

Note to my fellow old people: Take a chair. A heavily reclining chair. As the eclipse will be VERY high in the sky.

 

[1oldman2]

Note to my fellow old people: Take a chair. A heavily reclining chair. As the eclipse will be VERY high in the sky.

Thanks for the "Heads up"
And NASA is putting on a "Two month to the Eclipse" event.
https://eclipse2017.nasa.gov/save-date-june-21-2017

 

[OmCheeto]

Thanks for the "Heads up"
And NASA is putting on a "Two month to the Eclipse" event.
https://eclipse2017.nasa.gov/save-date-june-21-2017

Actually, I just doubled checked, and the eclipse will only be at 45° above the horizon where I plan on being at.
It looks like it will be at around 63° at maximum.

ps. I did some spectral testing on the 1st of June, and IMHO, it was a dismal failure.

The "rainbow" in the upper right hand corner is why I was interested in BillTre's "Very Dark Black" thread.
My redneck paper towel tube lined with black craft paper and held together with duct tap solar filter device seems to still be leaking light.

Which is a good thing, as it gives me time to research this some more, and maybe whittle something out of a tree branch, as the above device tended to fall off if the wind blew, or I moved the camera, or the camera decided to turn off and retract the lens, at which point the wind would blow it across my driveway.

And my brand new garage sale tripod is much more robust than the one I picked up last year. 1/3 the price, also.

pps. Here's another image of a solar spectrum:

The Flash Spectrum of the Sun [APOD]
Image Credit & Copyright: Constantine Emmanouilidi

Explanation: In a flash, the visible spectrum of the Sun changed from absorption to emission on November 3rd, during the brief total phase of a solar eclipse. That fleeting moment is captured by telephoto lens and diffraction grating in this well-timed image from clearing skies over Gabon in equatorial Africa. With overwhelming light from the Sun's disk blocked by the Moon, the normally dominant absorption spectrum of the solar photosphere is hidden. What remains, spread by the diffraction grating into the spectrum of colors to the right of the eclipsed Sun, are individual eclipse images at each wavelength of light emitted by atoms along the thin arc of the solar chromosphere. The brightest images, or strongest chromospheric emission lines, are due to Hydrogen atoms that produce the red hydrogen alpha emission at the far right and blue hydrogen beta emission to the left. In between, the bright yellow emission image is caused by atoms of Helium, an element only first discovered in the flash spectrum of the Sun.​

(a tad too large for PF)

But that bolded part just gave me confirmation of what I was already planning on doing. A video. Even though the resolution drops down to 640 x 480, I'm familiar enough with the camera now, that I know it takes a while to focus, and think about other things, before it finally takes a picture. Getting that shot with a dollar store auto focus camera strikes me as nearly impossible.

hmmmmm... I do have an old Canon A-1 sitting in the closet, and I do have that spare tripod from last years garage sale. Do they still make that silver based plastic "film" stuff, from the olden days?

ppps. I also found the one link that APOD mentioned interesting, as I may have just glossed over some of those facts in the past:

The spectrum of the corona.

... The green emission (at a wavelength of 530 nm) was discovered in 1869 and its origin remained a mystery for over 70 years. Because it could not be identified with any element known on the Earth, it was suspected that it might be due to a new element, tentatively dubbed "coronium." (Remember, that helium was first discovered in the solar spectrum and named after the Sun.) Eventually, however, the mysterious green line was shown to be due to thirteen-times-ionized iron, that is, iron atoms with 13 electrons stripped off! This was one of the first indications that the corona is extremely hot; indeed temperatures of several million degrees are required to strip 13 electrons from iron. The search for coronal heating mechanisms continues to this day...​

I've bolded all the thing I find really interesting, or did not know, or had somehow forgotten.

 

[jim hardy]

(a tad too large for PF)

cropped down to

 

[jim hardy]

and maybe whittle something out of a tree branch,

Don't overlook plastic plumbing fittings. All kinds of clever shapes in those bins .

the above device tended to fall off if the wind blew,

Rubber band around back of camera ?

the mysterious green line was shown to be due to thirteen-times-ionized iron,

Just how much iron is in the sun? I thought it was still burning hydrogen into helium.

 

[jim hardy]

Just how much iron is in the sun?

oops
EDIT This table turned out to have multiple errors so disregard it. I'm sorry about that, old jim
https://www.space.com/17170-what-is-the-sun-made-of.html

 

[Borg]

That chart makes me wonder how the fusion rates and quantities change as the sun burns through its hydrogen. As you get more helium, its rate of fusion with other elements increases plus, as the hydrogen quantities decrease, the radiant pressure changes which affects the fusion rates as the effective gravitational pressure increases. So many variables...

 

[mfb]

The interior gets a bit hotter and denser, increasing the fusion rate a bit and making the sun a little bit larger and more luminous. Eventually that process will accelerate and the sun becomes a red giant.

Fusion changes the core composition - the surface composition is a different thing.Apart from the helium->hydrogen process, all the elements in the sun come from its initial composition.

 

[Borg]

Apart from the helium->hydrogen process, all the elements in the sun come from its initial composition.

Yes, I should have said a star vs. the sun such that the heavier elements are only created in larger stars and only escape by way of a supernova.

 

[mfb]

Well, the Sun will create carbon later in its life, and a little bit of heavier elements.

 

[OmCheeto]

Can someone please confirm that the Iron % by mass in the Space.com in Jim's image is incorrect due to a missing zero.

Thanks!

ps. This was making me want to cry this morning, as I'm really getting tired of my bad maths...

 

[Helios]

My Magic Square of Eclipse Prophesy will predict solar eclipses on or near August 21st. All rows, columns, and diagonals will add up to 10085. There could be a few misses, but it should work pretty good otherwise. The square can be reset to any other eclipse on another year by an additive constant.

 

[mfb]

Can someone please confirm that the Iron % by mass in the Space.com in Jim's image is incorrect due to a missing zero.

Good catch. There are three mistakes.
Iron should have 0.003 by abundance (a factor 10 less), and 0.14% by mass (a factor 10 more). Sulfur should have 0.0015 by abundance (a factor 10 less).

@Helios: Where is the prediction? Where are August 23, 2044 or August 24, 2062? 24 August 2101 and 26 August 2147 made it in.
A few misses? You missed 2 out of 5 in the 21st century.

22nd century? 26 August 2109, 15 August 2110 (okay, 6 days), 25 August 2128, 15 August 2129 (6 days), 16 August 2156, 25 August 2166, 27 August 2174 (6 days), 26 August 2193, 16 August 2194 - out of these 6-9 only 3 are in.

The square can be reset to any other eclipse on another year by an additive constant.

We can get eclipses close to August 11 if we adjust add 1 everywhere to have the August 11, 2018 eclipse in the center? Then it would predict an eclipse around August 11, 2037. The last eclipse of 2037 is July 13, 2037. That is about as far away as it can get.

Where does this square come from?

Edit: The most common distance is 19 years, which is close to the length of the Saros cycles of 18 years. 9 years as half a Saros appears as well. 46 is the only other difference. 46=18+9+19.
Starting from 11 August 2018: 9 years later we have August 2, 2027. 19 more for 2046? Indeed: August 2, 2046. +19? August 2, 2065 - spot on. +46? 4 August 2111. +19? 4 August 2130. +46? 4 August 2176
I can't directly link it to Saros cycles and it misses various eclipses, but it looks like a pattern.

 

[jim hardy]

Good catch. There are three mistakes.

Well ! So much for space dot com as a reliable source.

 

[Helios]

@mfb This square should be good! So August 21, 2017 isn't the best for the center. I'll tweak it and put 1998 in the center. That's subtracting 19 years from every date. This changes the sum to 9990. All these are solar eclipses, with only two partials. It doesn't catch all eclipses, just the close and reliable ones. These I think are Y = 19, 65, 84, 130, 149, 168, 177, 223, 242, 261, 307, 326. and I made the square from these.

 

[OmCheeto]

Well ! So much for space dot com as a reliable source.

It looks as though they misabsconded the table from Hyperphysics.
Which they claim to have absconded with from a textbook: Fraknoi, Morrison & Wolff Table 14.2, Published 2000

Trying to find a free copy, I accidentally downloaded a 1200 page, 178 megabyte different text by the same authors: Astronomy, published in 2016.
They have a similar table with all the same elements, though the numbers have been revised a bit.
page 526(text book) or 536(pdf)
Table 15.2

Elem      % by #    % by mass
H         92.0        73.4
He         7.8        25.0
C          0.02       0.20
N          0.008      0.09
O          0.06       0.80
Ne         0.01       0.16
Mg         0.003      0.06
Si         0.004      0.09
S          0.002      0.05
Fe         0.003      0.14

Trying to find it, I ran across some really fascinating things:

Galileo didn't invent the telescope. He was just the first person to use it for astronomy.​

And just below table 15.2, they mention the following:

The fact that our Sun and the stars all have similar compositions and are made up of mostly hydrogen and helium was first shown in a brilliant thesis in 1925 by Cecilia Payne-Gaposchkin, the first woman to get a PhD in astronomy in the United States (Figure 15.3). However, the idea that the simplest light gases—hydrogen and helium—were the most abundant elements in stars was so unexpected and so shocking that she assumed her analysis of the data must be wrong. At the time, she wrote, “The enormous abundance derived for these elements in the stellar atmosphere is almost certainly not real.” Even scientists sometimes find it hard to accept new ideas that do not agree with what everyone “knows” to be right.​

Don't overlook plastic plumbing fittings. All kinds of clever shapes in those bins .

Good idea! I actually found one that fit. But the camera was not designed for the addition of auxiliary lenses, so it ended up not working. But I did devise something that will work. I'm almost ready!

All I need now, is a cardboard box.

1963. Interesting solution when you don't have solar filter material. Actually, I think this is a brilliant idea, for people who can't make it to totality.

 

[Seymore Proof]

What do you mean ...The points of Greatest Eclipse...will be at the opposite sides of Kentucky. The closest place to me would be in Idaho since I live near Salt lake. So would I be driving up there just to view an almost full eclipse or what?

 

[mfb]

Huh?
Everyone in the band will see a total eclipse. In the center it is longer than close to the edges. At Shelley you have a very short phase of totality, at Idaho Falls it is longer already, and between Rigby and Rexburg you have the longest totality.

The duration of the eclipse in the center of the band varies a bit as well along the band, but that is a smaller effect.

 

[OmCheeto]

What do you mean ...The points of Greatest Eclipse...will be at the opposite sides of Kentucky. The closest place to me would be in Idaho since I live near Salt lake. So would I be driving up there just to view an almost full eclipse or what?

per NASA's GLOSSARY OF SOLAR ECLIPSE TERMS;

"greatest eclipse - For solar eclipses, Greatest Eclipse (GE) is defined as the instant when the axis of the Moon's shadow cone passes closest to Earth's center."​

Don't feel bad. I had to look it up. As far as I'm concerned, it's an "eclipse nerd" term.

I don't think it will make much of a difference where you see it from, as long as you're at or very near the blue centerline.

As, the closer to the blue line you are, the longer totality lasts.

On the blue line near Idaho Falls, totality lasts 2 minutes and 18 seconds.
On the red lines, totality last about 1 second.

Driving all the way to Kentucky to be at the "Greatest eclipse" point, will add about 20 seconds to totalities duration.

Hardly worth the petrol, IMHO.

 

[OmCheeto]

...
I don't think it will make much of a difference where you see it from, as long as you're at or very near the blue centerline.
...

Unless of course, you are using NASA's map, and then you want to be near the red line:

https://eclipse2017.nasa.gov/sites/default/files/interactive_map/index.html

 

[tony873004]

Being near the edge has the advantage of longer diamond ring and Bailey's Beads and perhaps prominences. But it comes at the expense of totality duration and darkness of sky. Areas just a mile away from you are in your direct line of sight and experiencing direct sunlight.

Being far from the "Greatest Eclipse" has the advantage of giving you a longer shadow along the track of the eclipse, perhaps giving you a darker sky at mid-eclipse. You also don't have to strain your neck as much as the eclipse is lower in the sky. These advantages come at the expense of totality duration.

I got a campsite in Madres at their Oregon Solarfest. It's a 20 x 20 foot plot for my car and my tent. They've planned a large 3-day party complete with classic rock cover bands. We will get 2:03 of totality beginning at 10:19 am, and the Sun will be a comfortable 42 degrees above the horizon.