'Supermoon' Lunar Eclipse Coming Sunday

When and Where to Watch This Weekend's Total Lunar Eclipse Late on Sunday evening, September 27, the Earth will slide precisely between the sun and the moon, throwing the satellite into a rusty red shadow. This’ll be the fourth total lunar eclipse in two years, but that doesn’t make it boring. Quite the opposite—this week’s event will be the last in this rare tetrad, and the most dramatic.

That’s because this lunar eclipse coincides with another astronomical event: a supermoon. That’s what it’s called when the moon’s mostly elliptical orbit brings it closest to Earth’s surface—about 220,000 miles away instead of its average 240,000 miles. During this total lunar eclipse, the moon will appear about 14 percent larger and 30 percent brighter than Earthlings are used to seeing it.

And yes, it’ll also change color. The Earth doesn’t totally shade the moon; some sunlight trickles around the edges of the planet and gets filtered through the atmosphere, which only lets through light with longer wavelengths. That’s red. This eclipse also happens to coincide with the harvest moon, the full moon that falls closest to the autumnal equinox...