My story on sunsets July 17 had a sidebar on the green flash, that burst of color at sunrise or sunset that's over in an instant.

JIM GRANT Jim Grant of Shelter Island, who has captured the green flash with his camera at least 20 times, took this image from Pacific Beach.

The brief story wasn't intended to be the definitive piece on the atmospheric phenomenon, but several readers were upset that I failed to mention San Diego's own Andy Young.

“I'm probably right now the world expert on green flashes,” said Young, an adjunct professor of astronomy at San Diego State University.

No one is likely to step forward to argue.

Mea maxima culpa.

Young, 73, has been fascinated with green flashes for about 50 years, and he has been studying them scientifically for 10 years.

If you have a question about them, he's the one most likely to have the answer. His Web page, at mintaka.sdsu.edu/GF/, has probably already addressed your query, plus hundreds more that will never occur to you.

He gives detailed scientific explantions of such things as astronomical refraction, dispersion, “mock mirages” and several other types of flashes. He has tons of photos, flash simulations and links to other writings on the topic.

Young said it can be frustrating dealing with the many people who insist that green flashes are a myth.

“You still have people who say, 'That's impossible!' But if you understand the physics, it's perfectly plausible,” he said.

It would be impossible to pass along more than a tiny fraction of Young's green-flash knowledge. Here are a few key points, gleaned from a conversation with him last week, for people who would like to witness a flash:

It's much easier to see the flash with binoculars or some other type of magnifying lens, such as a camera, than with the naked eye. But even with the naked eye, you should be able to see several a year in San Diego – if you're not colorblind. People with red-green colorblindness will have a very tough time seeing a green flash.

To see the flash, you need a horizon that is below eye level. The ocean is a great spot, because it's guaranteed to be below eye level.

When the ocean water is warm relative to the air, the best viewing spot will be down near the surface. When the water is cooler, the best spot will be on an elevated bluff.

May, June and July are bad months for seeing green flashes locally because of the heavy marine layer. The flashes begin to appear with greater frequency in August. September and October are good months for spotting “mock mirage” green flashes, which Young explains on his Web page. The winter months are better for seeing “inferior image” flashes, which he also explains on the site.

If you wait until the sun is touching the sea horizon, it's perfectly safe to look at it. The atmosphere filters out all of the harmful rays. Looking directly at the sun when it's high in the sky can damage your eyes.

Flash follower

Jim Grant has become a sort of disciple of Young's. Grant's friends call him “the Greenie.”

It's an apropos nickname for someone so obsessed with the flash.

Most days, Grant, 52, can be found at the beach as the sun sets, trying to capture the fleeting phenomenon on film.

He has been aiming his lenses at the sinking sun on and off for eight years – fairly religiously for the last three. He recently bought a $700 Nikon camera, complete with 300-millimeter lens, that shoots four frames per second. That ups his odds of capturing the brief emerald light.

“Once you've seen enough, you can figure out if you'll have a good opportunity,” said Grant, who lives on Shelter Island. “I have had many shots where I think I had it, but it's bleached out yellow or gold. To get it on film, you have to have things just right. It can't be too bright or too dark.”

He says he has nailed the shot and captured the color at least 20 times. About 15 of those pictures are very good, he says. His shots hang at the Green Flash restaurant in Pacific Beach and Tower Two Cafe in Ocean Beach. Another is outside the director's office at the Royal Observatory in Greenwich, England.

Other Grant shots can be seen on Young's Web site. Grant attributes his fascination with the flash to Young, whom he met eight years ago. He showed the professor his first crude shot of the flash back then, and Grant has been trying for the ultimate picture since.

He has given his green flash photographs to many friends, but he has no desire to make money off his shots. He said he would “lose the joy” if he tried to cash in on his passion.

“When you can show them something like this, they get a little appreciation for creation, and nature and astronomy,” he said.

“It's a good show at the end of the day.”

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