Rainy eclipse

EDITOR’S NOTE: Because this column recounts an observation of the Sun without a filter, we sought the opinion of B. Ralph Chou, professor emeritus of the School of Optometry and Vision Science at the University of Waterloo, one of the foremost researchers in the field of eye safety. In his reply, he said, “The technique of observing the Sun by its reflection off water dates back several thousand years. It is quite safe because the reflection in the visible spectrum is of much lower intensity and the reflected flux of ultraviolet and infrared radiation is extremely small and therefore of no concern. Although the Sun’s image is bright, it is not hazardous for the brief observing times that the author used.”

I almost made it to the remote Norwegian island of Svalbard on March 19, 2015, to view the next day’s total eclipse of the Sun. But a tight connection, last flight, and other logistical nightmares ended my travels that day. So, I settled into a hotel in Oslo, where I awoke on eclipse morning to a gray sky and lots of drizzle.

As the time of first contact neared, however, breaks in the weather allowed glimpses of the Sun. So outside I went, armed with a camera and a solar filter — the latter of which I seldom used because I happily shared it with hotel staff and guests who were thrilled to watch as the Moon covered 86 percent of the Sun at maximum. At one point, I happened to look down at my feet and into a puddle where I saw the eclipsed Sun, naturally filtered by the water, surrounded by a glowing corona (an atmospheric one).

A ripple effect
The puddle acted like a mirror, reflecting the image to my eyes. The dark asphalt background combined with the thinning cloud acted as a natural filter (absorbing and scattering light), reducing the Sun’s brilliance by some 50-fold and making the eclipse comfortable to observe without optical aid.

As I watched the Moon’s dark silhouette sink its teeth into the solar surface, I noticed it had an irregular shape. This distortion is common to reflections tilted to the plane of sight. Imperfections in the water’s surface distorted the event, which I found fascinating. The minute undulations, some barely visible, acted like another layer of tilted mirrors creating all manner of optical effects, including crescents and other shapes in a glitter path and, at times, a crisp polygonal edge to the Moon’s silhouette.

Muddle in a puddle
The puddle view also revealed a beautiful aureole — the innermost ring of the colorful atmospheric corona. It consisted of a pale blue inner region (indicating scattering of blue light by tiny water droplets in the cloud) fringed by a smoky orange ring.

Usually, the aureole is indeed concentric with the Sun’s disk. But during a partial solar eclipse, the ring is concentric with the illuminated crescent, making the colored sphere appear oddly lopsided. You can view this effect more frequently when viewing a lunar crescent through passing altocumulus clouds.

Smoke & mirrors
Finally, I got a shudder when I saw what appeared to be a reversed aureole effect. When looking at the eclipsed Sun in the puddle, I saw the greatest extent of the aureole on the side of the eclipsed Sun when it should have been the other way around. It took but a moment for me to realize that this was an illusion created by a crescent-shaped cloud edge, almost concentric with the Sun, which obscured the greater half of the aureole.

The effect recalled a telescopic observation of the Skull Nebula (NGC 246), a planetary nebula in Cetus. It has a central star that appears off-center because the nebula’s eastern rim is exceedingly faint and fully one-quarter of the shell is all but invisible through small telescopes.

As always, go gently into the night (or the shadow-darkened day, if that applies), and let me know what you observe at sjomeara31@gmail.com.