The green flash appears as the sunlight disappears on the horizon as seen from Ocean Beach Pier on Jan. 16, 2017. Photo by Chris Stone
Green flash appears as sun dips on the horizon Jan. 16, 2017, near Ocean Beach Pier. Enlarged photo by Chris Stone

San Diegans were treated Monday to the rare solar spectacle called the “green flash.”

Brian Lada of posted a pair of San Diego shots of the sun briefly turning green as it dipped beneath the Pacific horizon. He took the shots from the beach next to the Hotel del Coronado, he said via Twitter.

Times of San Diego contributing photographer Chris Stone captured a “green flash” series from Ocean Beach at 5:08 p.m.

She used a Nikon D750 digital SLR camera with a 80-400 Nikkor lens and a 1.4 teleconverter — for a focal length of 550. The image was shot at 3200 ISO, speed of 1/3200th at F8, with a minus-2 exposure compensation on manual settings.

The shots here were unretouched except to straighten the horizon.

Many people have seen the flash, but few have gotten the picture. Indeed, in an online science posting Susan Borowski once said: “For some, catching a glimpse of it can be a lifelong quest.”

Four years ago Tuesday, LiveScience contributing writer Kim Ann Zimmermann told how Nigella Hillgarth, director of the Birch Aquarium at the Scripps Institution of Oceanography in San Diego, “got lucky one night.”

“I often work late and have developed the habit of taking photos of the incredible sunsets over the Pacific from the Aquarium,” said Hillgarth, now president and CEO of the New England Aquarium in Boston.

“One evening, I was snapping away and caught the green flash as it appeared. I was hoping for a green flash, but was very excited when one actually happened and I caught it!”

Andrew T. Young, a San Diego State University astronomer, maintains a page about green flashes.

“The basic cause of the color is atmospheric dispersion: refraction by air is larger at shorter wavelengths,” Young writes.

“So, at sunset, the refractive delay of the sunset is usually a second or two longer for blue and violet than for red. In general, then, the red image of the Sun (or of some miraged part of it) sets or disappears first, followed by yellow, green, blue and violet.”

A mirage expert as well, Young said: “There are still many loose ends to the Green Flash business” and posted a list of “unsolved green-flash mysteries.”

But Young says the green flash isn’t hard to spot — if you know how to look and where to stand. He suggests binoculars — and being cautious about bright sun.

“Here in San Diego, I probably see one or more flashes in 5 out of 6 sunsets over the ocean,” he says. “Without magnification, that would be more like 1 in 6.”

British Professor R.W. Ditchburn in the Jan. 15, 1959, issue of New Scientist debunked the belief the sky show was a mere legend or fantasy.

But he wrote: “In some Celtic folklore, on the other hand, the ‘green ray’ is said to give miraculous life-giving powers to certain herbs. It is also said that he who has seen the ray can look into his own heart and that of another, so that he will never make a mistake in love (or as a psychiatrist?).”