A veteran green flash spotter, Michael Robertson shares his insight into ideal green flash conditions.

This is what a green flash night, so long as the sun, which, as it sets, does not set behind that island. As it drops beneath those clouds, it will reveal either a clear horizon, or distant clouds we cannot see now.

Michael Robertson

I’ve seen the green flash so many times, I forget there was a time when it was a mystery to me. Before ever seeing it, I’d heard references to it and I wondered exactly what it was and whether it was real.

It is real. But it’s also a bit of a misnomer because it’s not a flash in the sense of bright light, it’s a flash in the sense that it’s over in a flash. It makes more sense to describe it as, “a green smear that you’ll miss if you blink.”

There are precise atmospheric conditions necessary to produce this phenomenon, and I’m not sure what they are, but I know that when I’m someplace with no mountains or clouds or too much haze obscuring the horizon and the setting sun, it’s likely I’ll see a green flash. To be clear, the sky can be solid overcast, but as long as there is a clear band at the horizon, conditions may be right.

Especially for folks living on the East Coast or the interior of the U.S., seeing the green flash is not easy. An ocean horizon to the west offers the best hope. Cruising in the Pacific offers plenty of open horizon opportunities. On the contrary, here in Ajo, we’ve got too much terrain to get a clear shot of the sun setting behind the horizon.

I saw a green flash soon before we left Fiji, while photographing the sunset, and decided to share exactly when it’s visible and what it looks like.