Naked-Eye Astronomy (Almost)

I had disliked the moon for decades. A bright moon washes out the “dim fuzzies” I love to photograph. For deep-sky astronomy, the only thing worse than moonlight is cloud cover. But on the evening of Saturday, March 7, I rediscovered Luna.

(I took this view the next night, using a digital camera and a zoom lens at 300 mm. I stacked five views, using astronomical software that allows stacking to reduce errors that are in individual images. If the moon were a clock, Copernicus would be at about 7:30 and Tycho about 4:30.)

Betsy the orange tabby and I were in the backyard bird-watching. More precisely, I was watching but she was watching and stalking. Since this was a bunch of alert birds that kept well away from her, I didn’t worry that I would have to jump to my feet and block a feline charge. So I enjoyed myself with the 9 X 63 binoculars I had bought years ago from Chuck Hards, amateur astronomer and telescope-craftsman.

The pine siskins, despite their diminutive scale, were the most aggressive at the feeders. They had scared off the goldfinches weeks ago and now were going after sparrows and house finches, lunging and chasing. We like to think of our yard as a peaceable kingdom where all creatures are welcome, but it’s not peaceful when siskins are around.

I loved watching the funny, coppery, head-bob quail, which strutted around imperiously. Keeping an eye on Betsy, one of the big males would chase other quail into the protection of the fir tree if they veered too close to her. The cat, however, was narrowly watching a siskin at a feeder that was among branches too high for her to reach. One quail stalked around so close to me that the binos couldn’t focus on him.

While this was going on the moon was rising higher in the blue afternoon sky. I realized that the air was perfectly clear and still, and that I was seeing the moon better than before.

I had often tried to glimpse a crater on the moon without using binos or a telescope, and I had always failed. Actual impact craters — as opposed to large bays and seas of flooded lava, which are called maria — were just too small. And I could only attempt it when the moon was in a relatively light sky, since to my eyes in the night, it is a jumbled mess of glaring overlapping blurs.

This time I could see the light circle of crater Copernicus against darker mare material. I used the binoculars repeatedly to verify it. Tycho was a standout in the binos, but I could not see it without magnification because it was surrounded by too much light ejecta. According to NASA, Copernicus is about 50 miles across.

I posted my little success on the UtahAstronomy Internet discussion board, and found that some others had been able to distinguish craters without resort to optical instruments. (Of course, it’s fair to use eyeglasses – if I couldn’t do that I’d see little of the moon. I could never do true naked-eye astronomy.)

Dave Bernson, president of the Salt Lake Astronomical Society, told me a few lunar craters seem distinct at the right phases.

“In particular, Tycho and Copernicus are large and bright,” he told me in an email note. “Tycho is most visible at full moon, when its rays are perhaps the brightest albedo feature on the moon, but the surrounding southern highlands are also rather bright. Copernicus is detectable more frequently because it is large and DEEP, and surrounded by dark maria as well.”

Kepler and Aristarchus are only slightly more difficult, he said, and seen best when the sun illuminates them from a low angle. “These two form a distinct triangle with Copernicus and are visible because of their bright, extended ray structure. Grimaldi, on the moon’s left limb, is shallow, but large and very dark.”

Some large structures like the Bay of Rainbows, the Sea of Crisis, the Sea of Tranquility and the Sea of Serenity, are technically the result of strikes by space debris, he said. But because they are immense basins that are flooded with basalt, I don’t consider them craters.

Have any of this blog’s readers ever observed a crater on the moon using nothing more powerful than eyeglasses? Or have any given it a try without success? Let us know by leaving a comment.

Now I am impressed with the moon. I plan do some moon gazing and photography on nights when I can’t search out galaxies due to the brightness of our natural satellite.

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