The United States has not seen a total solar eclipse sail from sea to shining sea in nearly a century. That means that next Monday, when the moon engulfs the sun in the sky, a new generation will experience a celestial extravaganza unlike anything else.

If you are one of these millions, prepare to feel changed forever. So say the eclipse chasers who venture great distances and go to extreme lengths to witness the ethereal occurrence.

“This is the most awesome astronomical event there is, period,” said Mike Kentrianakis, a veteran eclipse chaser. “You’ll never ever forget it.”

Mr. Kentrianakis has spent his life in pursuit of totality, the fleeting moment when the moon aligns perfectly with the sun and throws everything into darkness.