Perhaps you noticed the waxing crescent in the evening sky and thought, “Less than two orbits to go!” And perhaps you have given some thought to the eyewear you will favor for observing the annular solar eclipse on the afternoon of Sunday, May 20.
All responsible eclipse advice-givers (i.e., not me) are adamant that no matter what, you should never look directly at the sun during an eclipse. To which I have to wonder, haven’t these people ever looked at the sun? Can’t they close their eyes even now and make out the remnants of a long ago retinal branding? Well, perhaps they have and can, but it’s not the kind of thing you can advise someone else to go do, and it’s a severely limited method.
When I was a boy in sixth grade, my school was in the path of a solar eclipse’s penumbra. The authorized observation method for the day was pinhole projections onto paper on the ground. I didn’t altogether understand the concept well enough to firmly connect what I was seeing with what was up in the sky. Another boy came to school with a couple of dark glass rectangles that his father provided him from his welding equipment. This was a lot better than the pinhole projection, yet I find myself wanting something more for the upcoming event. I want the right amount of light attentuation that I can watch the eclipse as part of the surrounding landscape, to see sun and horizon and all about me; I want sunglasses. The advice-givers advise against this on the grounds that infrared and ultraviolet solar rays will punch through sunglasses, through the open pupils, and bake the retinas. With the right glasses, UV filtering is easily obtained, but IR is a trickier matter. No thin layer, like sunglasses, can block infrared. Standard glass is a fairly good IR filter, and also a bit of a filter of red as shown by the green tinge of slabs piled thicker and thicker. There is heat absorbing glass that is manufactured to do a better than fair job blocking IR, the sort that is used in a film slide projector to keep the light bulb from melting the slide. That’s what I have in mind to use, held up in my hand between the sun and my sunglasses.
For those who will be observing from further east, in New Mexico or Texas, another proven direct solar observation method is sunset. An oblique path through many hundreds of miles of atmosphere produces a squashed red oval that anyone can drink in bare-eyed. Whatever method you arrange, keep it handy to use again for the Transit of Venus two weeks later, the afternoon of Tuesday, June 5.