A total lunar eclipse is coming July 27—and at an hour and 43 minutes of visibility, NASA says it will be the longest eclipse of the century. But if you're in the US, don't plan on seeing it: It will only be visible from parts of South America, much of Africa, the Middle East, and Central Asia, CBS News reports. A lunar eclipse, which occurs when the sun, Earth, and moon line up so that Earth's shadow is cast on the moon, always happens within two weeks of a solar eclipse; in this case, there will be partial solar eclipses on July 12 and August 11. Those will be visible from Australia (July) and parts of Europe and Asia (August).