I am writing this well after the event, but I have a lot to catch up on! This one was definitely one of the highlights of 2017. A number of us had known about the eclipse for over a decade and the fact that totality would traverse King Mountain, a favourite hang gliding site. However none of us had really studied the details. Initially we thought it would be fun to fly through the eclipse, however after some research and consideration we realized; the 1.5 hour twilight build up of partiality would eliminate thermal activity, and likely make the air catabatic. On top of that, the one thing you want to see/enjoy is the corona, and you wouldn't get to see it since the wing would be in the way. Another interesting surprise was the shadow tracked west to east, as shown by the clip below.
An eclipse does not always have totality, both the orbit of the earth around the sun, and orbit the of the moon around the earth are concentric. In fact is entirely coincidence that the moon in it's orbit is roughly the right angle to equal the suns diameter at its' distance. This fact has surely blown the minds of astronomers past. Perhaps even new faiths were born of this. Some years in the future there will no longer be totality.
A few different spots were considered, for vantage point (proximity to center line, angle of shadow approach, without other hills or peaks blocking the shadow approach view, accessibility in the time frame from the morning. NASA helped with the size and velocity of the shadow relative to the ground.
There were a few good candidates, Borah peak, Jumpoff peak, Mckay peak, and Saddle mountain. In the end we decided on King, the timing was good eclipse started ~10:30 and supposedly it was a 3.5 hour scramble from the upper launch @ 8000feet msl to the top @ 10,600ft msl. It was only 15% off the center line (still plenty of totality).
The umbra (totality shadow) diameter was ~100km on this occasion, and with the shadowing approaching at ~40km/min, would yield about 2min 20sec. So far the math is working out. What would be really cool we thought, would be to watch the shadow approach at twice the speed of sound. Was it possible ? the edge would likely be quite diffuse, and I could not find previous evidence in the internet of it being something to observe.