Later this month, millions of Americans will be a tank of gas away from the total solar eclipse that will sweep across America from Oregon to South Carolina. It’s a moment that husband and wife Michael Zeiler and Polly White have been anticipating for decades. Together they’ve traveled the world chasing solar eclipses in places such as Austria, Indonesia and Gabon. In 2014, they launched GreatAmericanEclipse.com, a one-stop resource offering hundreds of maps of the eclipse and tips for viewing the event on August 21.

Zeiler works for ESRI, a mapping software company, and served as the cartographer on a 2015 eclipse-watching expedition to the islands of Svalbard in the Arctic Ocean. White manages the business side of GreatAmericanEclipse.com. The two talked to FiveThirtyEight about what has made chasing solar eclipses a lifelong obsession for them. An edited and condensed version of the interview is below.

Why is a total solar eclipse such a big deal? How does it compare to a partial eclipse or a lunar eclipse?

Zeiler: On a scale of 1 to 10, a partial solar eclipse is probably a 3. You’ll see a nibble of the sun taken out by the moon and you’ll need solar filters to look at it.

White: A lunar eclipse is effectively the reverse [of a solar eclipse]. It’s the shadow of the Earth projected on the moon. They’re quite beautiful to watch — especially the dramatic ones, when the moon can turn a dark red. But a lunar eclipse is nothing in comparison to a total solar eclipse.

Zeiler: A total solar eclipse has got to be a least a 1,000 [on a scale of 1 to 10]. For a couple of minutes it’s like you’re standing on the surface of an alien planet. There’s a 360-degree sunset all around you. You’re in a deep twilight — you’ll see the brighter stars and planets. But the sight that will be most amazing is the sight of the sun’s corona. There’s an incredible light show that happens in the sky around you — the remaining sunlight is electric. The corona beautifully frames the disc of the moon. The contrast makes for an incredibly black hole.

Together you’ve seen eight solar eclipses over the past 25 years. What keeps you coming back?

Zeiler: Eclipses connect you to the universe. In our daily lives, we don’t really perceive and understand the solar system in motion. But during a total solar eclipse, you see the solar system moving in real time. It’s an amazing cosmic coincidence that the moon and the sun [appear to be] just about the same size [in Earth’s sky]. We refer to it as the cosmic billiard shot. You’re lifted out of the Earth and sense that we’re part of a bigger universe.

White: You feel grateful after an eclipse. People celebrate — they’re wired, they’re partying. Most people hoot and holler, more than once people have cried. It’s that amazing, it’s that intense. Champagne is traditional among eclipse chasers.

It’s not, “You’ve seen one you’ve seen them all.” The corona is different each time. The inner corona is something we only really get to see during a total solar eclipse. The outer corona is the streamers and the flowers. Michael’s got names for all of them.

Zeiler: My first corona in 1991 had a pair of big beautiful wings to the side, so I call that the wing eclipse. The eclipse of 1999, in Europe, was very symmetric, like many petals. I call that the sunflower eclipse. The corona that we saw in 2013 in Africa was amazing because we saw two explosions of plasma being ejected from the sun.

White: Coronal mass ejections.

Zeiler: We saw those in real time with our binoculars. The one in 2015 in Svalbard, that was the lotus flower eclipse. The one in Indonesia, that’s the butterfly corona. Each corona will be indelibly imprinted in your memory.

You call yourselves eclipse chasers. Have you ever had to actually chase an eclipse?

Zeiler: So far I have a perfect record, eight out of eight eclipses. But during three of them I had to maneuver to get to clear skies. In Austria, I wanted to see the eclipse from near Munich with relatives in Germany. But the weather forecast the day before was rather poor, so I got in my rental car and drove to Vienna, which was near the path. That morning I drove past lots of crowds of people gathering to see the eclipse, but the weather was still patchy. I kept driving and driving until I got to the border of Hungary and I couldn’t drive any further. I stopped only about 10 minutes before the event. Luckily I had driven far enough, and I saw the glorious eclipse in a farmer’s field.

What are your plans for the eclipse later this month?

Zeiler: Our plan is to drive to Casper, Wyoming, with part of our family. Casper is a great location because it’s got very good weather odds and it has highways several hundred miles to the east and west that stay fairly close to the center of the path of totality. We’re going to have tents and sleeping bags in the car and we’ll strike wherever the optimum location is. My daughter and her boyfriend are going to be climbing the tallest mountain in Wyoming, which is Gannet Peak in the Wind River Range. If they’re successful, they’re going to have the amazing sight of seeing the moon’s shadow racing across the landscape toward them, enveloping them in darkness and then proceeding out to the east.

You can use the Great American Eclipse interactive map to find viewing events along the path of totality.

Read more about watching an eclipse.