Charles Deehr will never forget his first red aurora.

Under the crimson sky, he was sure of two things: he and Tone were seeing a great red aurora, and he would ask her on another date.

Charles — Chuck to his friends — was a space-physicist and aurora forecaster at the University of Alaska Fairbanks for most of that time.

Fringes of red and blue hanging from aurora curtains — the result of particles from the sun reacting with nitrogen in the upper atmosphere — happen often, but the great displays that flood the sky with diffuse red light are rare.

Red aurora displays happen so high in the sky that they are often the only form of aurora ever seen by people in the mid-latitudes.

37, a great red aurora showed itself to the citizens of Rome.

Deehr and his date witnessed one of the most spectacular displays in 1958.

A rare red aurora over Alaska in February 1958.

“To get a pure red aurora, you need two things from the sun,” Deehr said.