[For those of us too broke or cheap — or yes — to have gone to totality to see the eclipse, Stephanie Osborn provides a lovely recap.]
The Great American Eclipse from the centerline
By Stephanie Osborn
(All images in this article courtesy Dr. Robert R. Murphy, M.D. and Patricia Murphy, R.N.)
On the afternoon of 21 August 2017, the Moon entered its “new” phase at the exact same time that the Sun, Moon and Earth experienced a syzygy.
It’s called a solar eclipse.
This would be my second total eclipse, but my first TRUE total eclipse: when I was in graduate school studying astronomy, a total annular eclipse (an eclipse which occurs with the Moon at apogee, the farthest distance from Earth, means it doesn’t completely cover the solar disk, and leaves a ring, or annulus, of visible disk) tracked across Atlanta GA one summer in July (if memory serves). So one of my fellow astronomy graduate students and I had picked up and made a road trip from Vanderbilt University in Nashville to Atlanta, with full blessing of our professors, as well as loaned portable telescopes equipped with objective solar filters. That in itself was an adventure, but today I want to talk about the most recent experience.
Having planned ahead, we spent the night at my parents’ house in the country a little south of Nashville TN. On eclipse day, I found myself, ISO-certified eclipse glasses in hand, with several family members and any number of new friends at the small Smithville TN Municipal Airport, FAA Identifier 0A3, elevation 1084.3ft, latitude 35º 59’ 07.6” N, longitude 085º 48’ 32.8” W. Normally this small regional airport would be closed on Mondays, but it was open especially for the astronomical event we were all there to witness. We were a stone’s throw from the center line, and per my Solar Eclipse Timer app (ain’t technology great?), would experience fully 2 minutes and 35 seconds of totality around 1:30pm local time (Central time zone).
By the way, for those who don’t know, the Moon’s shadow during a solar eclipse travels in the near vicinity of 1000-1200mph on average, though depending on the geometry and the curvature of the Earth under the eclipse path, it can go as slow as some 7-800mph and as fast as 8000mph or more. For this eclipse, maximum velocity occurred as the shadow was crossing the west coast in Oregon, at around 2,200mph; minimum velocity — thus longest duration — occurred in Kentucky and Tennessee, where it slowed to just over 1,300mph. It was already speeding up again by the time it crossed the East Coast in South Carolina, at nearly 1,500mph.
The maximum totality duration possible was 2 minutes, 40 seconds, which occurred very near Hopkinsville, KY, which area is the stomping grounds of my youth… but which was over an hour of additional driving, with nowhere to stay overnight, as my family has moved away from the area. Our duration of 2:35 was therefore not shabby at all.
We arrived at the airport around 10:00amCDT and set up chairs, a small awning, and a table with plenty of food and drink (sandwiches, chips, a veggie tray, several kinds of dip, cookies, brownies, iced tea, lemonade, water — all well chilled; yes, we know how to tailgate!), which we gladly shared with the airport staff and volunteers, as well as several emergency responders stationed at the airport. The airport expected up to 75 planes that day, all there for a special eclipse “fly-in.” I’m not sure we had THAT many aircraft, but I’d say we had easily in the near vicinity of 50, and the planes averaged 2 persons per, some more, some less. A few larger planes carried entire contingents of a dozen or more. Observers ranged from as near as Knoxville TN, to western Texas and beyond. I’m pretty sure I heard someone mention they flew in from Ontario, Canada.
The morning dawned bright and clear, with no rain forecast, but there was some cloud cover, mostly light high cirrus haze and some pop-up-type cumulus. As the day progressed and the heat increased, the percentage of cumulus cloud cover increased substantially.
Eclipse timings are defined by four principal points: first contact, second, third, and fourth contacts. These are geometrically defined; first contact is when the leading edge of the Moon first “contacts” the near side of the solar disk; this is the beginning of the eclipse event. Second contact is when the leading edge of the Moon first “contacts” the FAR side of the solar disk, and this marks the beginning of totality. Third contact is when the TRAILING edge of the Moon first “contacts” the near side of the solar disk, and this marks the end of totality. Fourth contact is when the trailing edge of the Moon “contacts” the FAR side of the solar disk; this marks the end of the eclipse event.
First contact was scheduled for 12:00:44pm CDT.
The temperature at the time of first contact, according to my weather app, was 94ºF. Cloud cover was substantial, and partly obscured observations of first contact, but not enough to prevent the observations being made. First contact occurred at roughly two o’clock on the solar disk (meaning, if the Sun were a clock face, the Moon touched it at the numeral 2).
The eclipse proceeded steadily after that. Little was noticeable at first, though the “bite” taken out of the Sun grew larger and larger. At about the halfway point, the ambient light got “funny” — the sky grew marginally darker, and there was a sensation as if the illumination was dimmer. My impression is also that it tends to be slightly skewed to blue shades, but that may be only my eyesight, and is subjective.
As totality approached, we began to realize that the cloud cover was diminishing steadily, most likely as a result of decreased heating/evaporation from the ground providing for less and less water vapor for cloud formation. However, there was cloud cover around the horizon except in the direction of the approaching lunar shadow (roughly NW), where a distinct gap, surrounded by two cloud banks, made itself apparent. The temperature was also dropping noticeably; with 45 minutes still left to totality, my weather app indicated we were already at 90ºF, and it was continuing to drop. At 30 minutes to totality, it had dropped to 88ºF.
As the sky darkened, the entire horizon took on the colors of sunset. I made a pinhole camera by punching a hole in a paper plate, to show some of the children that had gathered to watch with their families; it showed the progressing solar crescent quite nicely. At only 15 minutes to totality, we spread out a white quilted tarp for observing the diffraction-pattern “snakes.” There was nothing left of the cumulus clouds overhead, only a faint, high cirrus haze, which did not obscure viewing to speak of.
Second contact, and onset of totality, was scheduled for 13:29:20 (1:29:20pm) CDT. I called out a countdown to totality for the lay observers. Just before full totality was reached, my father spotted the diffraction pattern on the tarp, reporting that it lasted for a scant five seconds. Some observers with large camera optics reported Baily’s beads — the last glimpses of the Sun through mountain valleys on the rim of the Moon. My aunt captured the “diamond ring,” an illusion produced by the last rim of the solar disk still visible at the moment that the corona begins to become visible. (This also occurs at the end of totality; she captured both.)
At the beginning of totality, some wags at the eastern end of the airport’s E/W runway began setting off a fireworks display in celebration; it appeared to be electronically controlled and quite the nice display, what little I saw of it. I suppose, had I been sitting behind it so I could see it against the backdrop of the eclipse, I might have enjoyed it more. But I had no problem with the already-jubilant atmosphere to which it added a bit of ambiance.
The sky at the airport was clear and cloudless, though there was still a broken ring of clouds around the horizon. The minimum temperature I observed on my weather app was 81ºF; it was quite comfortable and a slight breeze appeared to spring up. (Temperatures can drop during totality by up to 25ºF; the general consensus of the observers was that the weather app was lagging badly and may not have displayed the actual low temperature. We felt it was likely in the mid-to-upper 70s during totality.) At this point, unaided viewing was safe and possible, no protective devices needed.
The sky overhead was dark — enough so that the runway lights automatically switched on, as did the light illuminating the wind sock, and all street lights visible in the vicinity — and Venus was easily visible to the WNW of the eclipse; I also caught averted-vision glimpses of Mars (currently on the far side of the Sun from Earth in its orbit), and of Mercury (my first ever view of Mercury; I have never been in a location with unobstructed horizons whenever Mercury was at maximum elongation and therefore visible at sunrise or sunset). The entire horizon, the full 360º, took on a post-sunset look, with the deep orange right at the horizon rapidly fading through yellow and green into deep blues; a brief chat with an amateur astronomer confirmed my impression that the sky appeared to be some 45 minutes after sunset.
Given our position in the middle of the tarmac, there was little in the way of animal activity to observe; however, the ubiquitous cicadas ceased chirping, as did the birds, and save for the fireworks on the far edge of the airport, and a few human murmurs of delight and awe — and my occasional call-out of information — the experience was almost eerily quiet.
Third contact and the end of totality occurred at 13:31:55 (1:31:55pm) CDT. Again, I called out a countdown for lay observers, to ensure eye safety; at only a couple of seconds to end of totality, I called out, “GLASSES ON!” and just as I donned my own, I saw the outgoing “diamond ring.”
The sky began to lighten as rapidly as it had darkened. Temperatures, however, remained depressed according to my weather app, though it soon began to feel quite hot once more. I suspect that there may have been a lag in the app, though I cannot verify it. At any rate, according to the app, an hour past third contact, the temperature was still only 84ºF. The sky did remain amazingly clear except for that same high cirrus haze. Only in the last half-hour before fourth contact did the cumulus clouds begin to re-form. Ten minutes prior to fourth contact, the weather app showed the temperature had risen to 88ºF.
By this point, all was almost back to normal with the sky and the world, at least in our part of it. The casual observers had begun departing at the end of totality, and the airport became relatively quiet, except for a few hardcore observers like myself, determined to stick it out until fourth contact, and the airport staff. Every thirty seconds or so for the first hour after third contact, an aircraft took off. My family, not quite as hardcore as their professional astronomer, began to break down our “tailgate” and load up, leaving the chairs and the awning for last, to provide rest and shade as the temperatures ramped back up.
Fourth contact, the end of the eclipse, was at 14:55:52 (2:55:52pm) CDT. The weather app still showed only 88ºF, but it felt considerably hotter, so I suspect it was still lagged. Cumulus cloud development was still underperforming, though it was gradually starting to rebound.
My estimation of the temperature as fourth contact passed would set it being at least the equivalent of the temperature at first contact: 94ºF. It did get marginally higher than that as the afternoon waned, though not by much. My estimates indicate it may have reached as high as 96ºF at Smithville TN.
Once fourth contact passed, we packed up the chairs and the awning and headed out, thanking our hosts along the way and donating to the airport’s upkeep. (It’s always courteous to help out the hosts.) We had an hour to drive to reach my parents’ house, where we took advantage of the facilities, as well as the air conditioning and ceiling fans. By the time we reached their house, the cumulus cloud cover had already reached and marginally surpassed its previous, pre-eclipse extent.
We allowed about 15-20 minutes to cool off in the excellent air conditioning, then headed home to Huntsville AL. So swollen by eclipse chasers was the traffic, however, that the nominal 1:45 drive took fully 2:40 to travel; the first leg of the drive, normally taking 20 minutes, took a full hour. Needless to say, we were glad to be home.
But I don’t regret the traffic, the long hours, the heat — any of it. Already scientific discoveries are starting to flow back from the data obtained during the eclipse, and much is being learned about such matters as the solar corona, how it behaves, and why it stays so hot (the corona has a temperature of several million degrees Celsius, whereas the photosphere, or visible “surface”, is only about 6000ºC).
The memories? Well, those are priceless.
Stephanie Osborn, award-winning author, is a 20+-year space program veteran with multiple STEM degrees. She has authored, co-authored, or contributed to 35+ fiction and popular science books, including The Weather Out There Is Frightful: Solar/Space Weather and You; Burnout: The mystery of Space Shuttle STS-281, the Displaced Detective series, and the new Division One series.