"It is such an incredible, sensory-overload kind of event," he told AFP.

Once it was over, he said he "immediately started thinking about future eclipses."

Espenak, now 65, is a retired NASA astrophysicist who goes by the moniker "Mr. Eclipse."

He has been to 27 eclipses, and seen 20 of them -- cloudy weather interfered with the rest.

Each one is unique, he says -- the way the twilight falls in the middle of the day, casting shadows on the Earth; hearing birds return to their nests; feeling the temperature suddenly drop.

The most memorable, he says, was an eclipse he traveled to in India in 1995 with about 35 other people.

One of the women in the group became overwhelmed -- she said she'd waited 25 years to see an eclipse, and wept over how it had gone by so fast, lasting just 41 seconds.

"We stayed in contact," Espenak said. "And to make a long story short, we got married."

When the so-called Great American Eclipse marches across the country on Monday, Espenak plans to be in Wyoming, operating 17 different cameras.

His advice for first-time eclipse-watchers?

"Don't do what I do. Don't take any pictures. Just watch it and enjoy it. There is so much to see," he said.

World record-holder

Most people who see an eclipse will experience just a minute or two of darkness, but in 1973, Donald Liebenberg set a world record when he rode the Concorde jet and chased an eclipse at supersonic speed.

From the cabin of the aircraft at an altitude of 60,000 feet (18,200 meters), his view of totality -- when the Moon's shadow completely blocks the sunlight -- lasted 74 minutes.

"The corona is so brilliant especially when you are above most of the water vapor and the other scattered light problems in lower altitudes," he said, recalling the deep purple sky.

Now 85, Liebenberg has spent more than two and a half hours of his life in totality, longer than anyone else on the planet.

He has traveled to Indonesia, Turkey, South Africa and Zambia, among other places, and seen 26 eclipses so far.

"Looking forward to the 27th," said Liebenberg, an adjunct professor at Clemson University in South Carolina.

"This one is special in the sense that it will occur over my house. I will be in my driveway instead of traveling thousands of miles."

Frequent flyer

Glenn Schneider, an astronomer at the University of Arizona, saw his first total eclipse when he was 14, and recalls a sensation of being frozen in time.

"I realized that this was the start of something that had changed my life, that I was going to have to see the next one. And the next one," he said.

"It almost sounds like it is an addictive phenomenon and it is. You should warn people of that."

Total solar eclipses happen on average about every 16 months somewhere on Earth.

Schneider has missed only a handful.

He still laments "the one that got away" -- an eclipse he missed in 1985 that brushed the coast of Antarctica.

But he has managed to get himself in the Moon's umbral shadow 33 times so far.

"I save my frequent flyer miles for eclipses," he said.

And now, the time between eclipses is "sort of a mundane reality," he said.

He has plans for every future eclipse, including one at sunrise over New York in May 2079 when he would be 123 years old.

"I don't think I am going to make it but I've left information for my daughter for her to go and see it," he said.

For Schneider, it's not just the view, or the scientific interest he has in the phenomenon.

"We are talking about a very visceral, emotional connection," he said.

"You really get a sense of celestial mechanics in action." To experience an eclipse "gives you a sense of perspective that you don't get any other way," he said.

"How insignificant we are compared to the whole system. How inconsequential some of the struggles we have with politics and the nonsense going on in our daily lives," he added.

"When the grand scheme of the solar system is played out in front of us, it's a humbling experience."

-AFP