I love the night sky, especially what’s visible with the unaided eye, and I love sharing that enthusisasm, whether it’s behind the controls of the Hatter Planetarium or way back in my days as a summer camp naturalist. But we suffer from swarms of overhyped headlines about sky sights. I am not talking about the outright social media fakes (“Mars will be as big as the moon,” etc.), but instead substantially correct information that may earn clicks but inevitably disappoints under the real sky.
Here’s one from this week, from a well-regarded media source: “A full moon, lunar eclipse and comet all in one night?” That sounds flippin’ amazing!! So let’s break it down:
Full moon and lunar eclipse. As you may know, this is no coincidence. A lunar eclipse can only occur at the full moon, just as a solar eclipse can only occur at the phase of new moon. That’s how the geometry works. Even reading the full text of the particular article above does not reveal that fact.
What kind of eclipse? This one is penumbral, meaning that the moon only enters the earth’s outer shadow. At no time is the sun completely blocked out from the moon’s point of view. Observant people will see a dimming on one side of the moon. Read a quality article here. If that’s what you expect, you’ll be happy you looked. Next total eclipse of the moon completely visible from Gettysburg? January 21, 2019.
Comet 45P. At seventh magnitude, it’s not visible to the unaided eye. In binoculars, it will look like a faint, green smudge, assuming you know exactly where to point the binocs. And as the Sky and Telescope article in that link makes clear, it is not a very easy object, and the light from the afforementioned moon will make matters worse. The good news is it’s not a one-night proposition. So if you’re up for the callenge, here’s that link again. But the bottom line is it’s something hard to see, not a “grab the kids” moment.