The Moon has a bright companion tonight: Aldebaran, the eye of Taurus, the bull. Skywatchers across much of the United States won’t see the star during part of the evening, though, because it’ll be hidden behind the Moon. The best view of that disappearing act comes from the northeast.

Even when it isn’t covered up, though, Aldebaran might be tough to spot through the Moon’s glare. The Moon is so bright that it can be hard to look at, especially from a dark skywatching location.

The Moon looks so bright because it’s a big, close target. In reality, though, it’s quite dark — it reflects only about 12 percent of the sunlight that strikes it.

Just how bright the Moon looks is important for folks who operate Earth-watching spacecraft. They sometimes use the Moon to calibrate their instruments. But no one has cataloged how bright the Moon looks at different phases and viewing angles. So scientists have to look at the Moon from space and the ground at the same time to get a good match.

But scientists at the National Institute for Standards and Technology have launched a project to measure the Moon’s appearance at just about every set of circumstances, in multiple wavelengths.

They’re using a small telescope in Maryland to look at both the Moon and at special artificial light sources. And next year, they’ll move the project to Hawaii. The observations should provide a good catalog of the Moon’s brightness, no matter how you look at it.

Tomorrow: Bright lights in the holiday sky.

Script by Damond Benningfield