Why your picture of the eclipse might have a little blue crescent hidden in it
On Monday, the entire US got to see a solar eclipse.
During the event, many people turned their cameras to the sky to get a snapshot of the eclipse in all its glory.
It was safe to take a picture through a smartphone, though the photos didn't get the NASA-level quality you'd see from an angle lens.
Instead, the photos tended to show the sun blown out in a blaze of light - not the crescent shape of a partial eclipse. But in some photos, a crescent did appear; it was just far from the actual sun and looked blue. You can see a clear example of this in the photo on the right, which was taken by Business Insider's Emily Cohn near New York's Flatiron building.
The effect is a "lens flare," which happens when a camera is exposed to a bright light. In response, the lens captures some of the light as a reflection. Lens flares generally show up as little dots or circles, but during an eclipse they appear as small crescents.
Another crescent-shaped lens flare is visible in a photo tweeted by Senator John McCain, which his staff captured near the US Capitol.
The same effect happened when Business Insider's Rebecca Harrington snapped a picture of the sun through welding glass. This time, three crescent suns are visible because of lens flare.
If you were hoping to capture what the eclipse looked like from your location, the crescent reflections that come out as lens flares are actually a pretty good representation. They are similar to the projections you might have seen through leaves, pinhole cameras, or even your fist.
