The Great American Eclipse of 2017
Eclipses occur on many planets, including Jupiter and Saturn. But a total eclipse is an extremely rare phenomenon that as far we know only occurs on Earth. What luck we have!
Why is this unique to Earth? For a total eclipse to occur, the apparent diameter of the moon must match the apparent diameter of the sun, each about 1/2 degree viewed from Earth. When both apparent diameters match, the sun's body is completely masked during an eclipse, for a brief moment, exposing the sun's corona, the super hot plasma (> 1,000,000 °K) escaping into space. If the moon is too small, a ring of the sun remains visible, and its brightness blots out the corona. If the moon is too big, the corona is not visible. In that case, only a partial solar eclipse is visible.
By pure coincidence, on Earth the apparent diameter of the moon and the sun match exactly, giving us the chance to experience from time to time a total solar eclipse. This will change in a few million years when the moon's orbit change as it slowly moves away from Earth. But for now, we can enjoy this awesome spectacle.
In order to experience and capture the total eclipse I drove from San Francisco to the border between Oregon and Idaho, in the path of the eclipse. After scouting around for a few days, I found a farmer's field which I liked for its open vista, clear skies and good weather forecast. I was joined by a dozen or so travelers, some having made the trip from as far as Los Angeles and Seattle. I was the only one taking pictures, though: unless you're a photographer, I think it's best to experience the phenomenon without having a camera getting in the way.
The following picture shows the partial eclipse as the moon starts to cover the sun. Clearly visible on the sun are several sun spots: they are areas of the sun's surface that are slightly cooler due to variation in the magnetic field and from which solar flares and coronal mass ejection often start.
This next picture is the totality, when the moon matches exactly with the sun, making the corona brilliantly visible.
The next two pictures are the "diamond ring" formation when the sun starts to peak out under the moon. In addition to the corona that surrounds the sun, you can clearly see on the top and right side of the sun several solar flares. How amazing is that!?
These pictures were shot with a Canon 5Dsr with a Canon 100-400mm ƒ/4.5-5.6L lens with a Canon 2x extender, a Really Right Stuff tripod, and a Solomark solar filter with a Baader Planetarium film.
The pictures of an eclipse are an awesome sight, but they don't do justice to the experience: the light fading during the partial eclipse, the colors in the landscape changing into weird hues, the temperature dropping and the awe inspiring sight of our familiar sun turning into a black hole surrounded by a brilliant crown.