2017-08-07 – It was probably 1994. I don’t know that for sure, but when I look for partial solar eclipses in the Chicago area, May 10, 1994. I was working at CCH in Riverwoods, IL at the time. I remember warm weather and a mid-day event. I worked at that location from 1986 to 1996 and there aren’t too many solar eclipses.

My job was writing for a couple of tax law research products. We were in the midst of the transition from print-based to computer-based products. Indexing our work-product was key, so lawyers and accountants could find what they needed. In the old days, we used actual, physical index cards to sort the tens of thousands of entries, which were then printed as an index. Key word searches came later.

Index cards were important on the day of the eclipse. Two index cards were needed to make a viewer that would enable you to see the partial eclipse. We made a hole in one of the cards and used it to cast a shadow on the second card. The shadow of an index card is, of course, rectangular. But the pinhole in the one card allowed an image of the sun to be to be cast upon the second card.

You could do that today, but the image would be entirely unimpressive. It would be nothing more than a small circle. You might think that the shape if the small light was the shape of the pinhole, but you would be wrong. The small circle is the shape of the sun.

The fact that you are imaging the sun doesn’t become really obvious until you do it on the day of a solar eclipse. If you use your index-card imager, you’ll see an incomplete circle as the moon progressively blocks the direct sunlight. Your image changes as the eclipse progresses. We were working that day, but we ran outside periodically to check on the progress of the eclipse. Click here to see the progression we saw (though, our images were somewhat dimmer than this).

This eclipse was fully visible somewhere downstate. I had given some thought to taking the day off to drive there. But the eclipse was going to be annular eclipse, which means that the moon was further from the earth than average with the result that its apparent size would be smaller than the apparent size of the sun. So not all the sunlight would be blocked. This forms a “ring of fire” but without the proper viewing equipment, the event would be entirely unspectacular. I just had index cards. Even so, I might have still taken the day off, but was expected to be cloudy

Later this month, August 21, to be exact, another solar eclipse will be coming to downstate Illinois. This eclipse will be a total eclipse. And the path of totality crosses from the West Coast to the East Coast (not just through Illinois). I plan to be on a vacation road trip on that day and we will be able to see the totality near Casper, WY. No index cards this time. I’ve order special glasses to allow us to look at the sun without burning our retinas and going blind.

And since we will see the totality of the eclipse, we expect to be able to take the glasses off and look directly at the corona of the sun, which is normally not visible to us because of the sun’s brightness. That will last a minute or two, depending on exactly where we end up stopping within the 60-mile wide path of totality. After that brief time, the moon will begin to pass away from the sun and we’ll put the glasses back on for as long as we still want to look.