Eclipse, supermoon on May 26 is celestial event of the year — The Know

Skygazers are eagerly anticipating what figures to be the celestial event of the year next week: the coincidence of a lunar eclipse with a supermoon, shortly before the moon sets over the mountains. We’ve got all the info you need to make plans for viewing it, including some thoughts on where to watch.

Events are set to unfold early Wednesday morning. If the sky is clear, early-rising observers can see the partial eclipse begin at 3:44 a.m., progressing into full eclipse from 5:11 a.m. until 5:25 a.m. Sunrise will come at 5:36 a.m., and the moon will set at 5:43. All of this will occur to the southwest.

John Keller, director of the Fiske Planetarium at the University of Colorado, recommends getting in position well before the total eclipse begins to fully enjoy the show. That way you can watch the earth’s shadow moving across the moon. It will be halfway across the moon at about 4:20 a.m.

“It’s going to be really pretty,” Keller said. “Having the horizon will accentuate the supermoon and the eclipse.”

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“Supermoon” is not a scientific term. It’s a popular name referring to full moons occurring when the moon is relatively close to the earth, thus visibly larger than normal. Some observers say there are two a year, following in successive months, while others tout three. But there’s no dispute about this one. It will be the closest full moon of the year at 222,048 miles from earth (16,800 miles closer than the moon’s average distance).

In a sense, the moon at eclipse next week will feel like it’s closer than it appears. Confused? Full moons always appear bigger when they are near the horizon, but scientists tell us that is an optical illusion. The moon at eclipse that morning will be the same size as when it was overhead hours earlier.

“It’s a combination of an optical illusion and the actual size of the moon,” Keller said. “The supermoon can be up to 10% bigger than a non-supermoon. That is a real effect, the moon is ever so slightly larger. But when the moon is directly overhead, there is nothing else around it except for stars. It’s having that perspective of the moon on the horizon, with stuff in the foreground that we know is big, making the moon look bigger.”

The illusion isn’t happening in your eye. It’s happening in your brain.

“It’s cognitive,” Keller said. “It’s not happening at your retina. If you took the size of the moon on your retina at moonset and the size of the moon on your retina when it is at zenith, it would hit the same number of rods and cones on your retina. But your brain takes that signal and changes that into an understanding of what it is seeing.”

Regarding where to observe the eclipse, there are some considerations to keep in mind. Keller plans to hike a peak near his home in the foothills near Boulder, which will give him a perspective of the eclipse happening over the Indian Peaks.

But keep in mind, you want an unobstructed view of the horizon to the southwest. If you pick the wrong spot in the foothills, you could miss the whole show.

There’s another drawback to taking positions on the western fringes of the metro area or in foothills. Daily sunrise, sunset, moonrise and moonset times are calculated against a flat horizon (think: a sunset over the ocean). When topography like mountains intervenes above that, actual moonsets and sunsets occur earlier than the official lunar and solar data says.

So, while vantage points for the eclipse in the foothills could be especially dramatic, the moon may appear to set there before the total eclipse ends.

The better option may actually be viewing from the metro area. And the best spots may be in the northern metro area with unobstructed views of Mount Evans. From that perspective, the eclipse drama will unfold over a beautiful fourteener.

A final piece of advice: Be in position well before the total eclipse begins. Keller plans to be in place about 4:45 so he gets to see a half hour of the moon in partial eclipse before totality.

“If people go out at 5, they will see the lit section disappear as it goes into totality at 5:11,” Keller said. “You’re going to see that little limb of brightness that’s still visible, and then it’s going to get much darker when it goes into totality. There is no direct sunlight hitting the moon after 5:11. All you’re seeing is the refracted sunlight going through the atmosphere, the reds of sunrise that are refracting and bending around the atmosphere, making the moon glow red.”

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