Annular Solar Eclipse of 20 May 2012

Annular eclipses occur because the Moon isn't in a perfectly circular orbit around Earth, and the Earth isn't in a perfectly circular orbit around the Sun. This means that the angular sizes of both bodies varies slightly. If a solar eclipse happens when the Sun is a bit nearer, or the Moon a bit farther, the Moon might not fully cover the Sun at totality. In that case, we will see a ring (an "annulus") around the Moon, and it won't get dark enough to see the corona. While not as impressive as a total eclipse, it's still very pretty.

On Sunday, May 20, 2012 a fine annular solar eclipse traced a path from southeast Asia, across Korea and Japan, over the Pacific, and in the southwest U.S. Although this would have been an nice partial eclipse from Cloudbait, I traveled south to Albuquerque to catch it right on the centerline.

I found a nice spot to set up along the base of Sandia Peak- a little above the city with a good view of the western horizon. That was important, because from this location the Sun would set while still partially eclipsed, so I wanted a good low view of it. At totality (in this case, when the Moon was centered in front of the Sun), the lighting became very odd. Besides being darker outside than felt right for the height of the Sun, shadows were strange. This is because they were being cast by a ring of light, not a disc like usual.

I set up a Coronado H-alpha solar scope which I used visually (there were some very nice filaments and prominences showing that afternoon), and my trusty Canon 300D camera with a 500mm Celestron Maksutov lens blocked with a glass solar filter.

Right at sunset, with the solar filter removed, I captured what appears to be the well known green flash phenomenon (caused by atmospheric dispersion)- not at the top edge as usual, but on the eclipsed limb.

Here's the full sequence from the beginning of the eclipse to sunset, covering about an hour and a half. The eclipse was still in progress as the sun set, so you can see the horizon cutting off the partially eclipsed Sun at the end.

Short animated sequence, from the beginning of the eclipse to sunset.