Space enthusiasts in certain regions of the world will get free seats to a potentially once-in-a-lifetime event on the celestial stage later this month.

On July 27, lucky stargazers will see the longest total lunar eclipse of the 21st century ― also known as a blood moon. The nearly two-hour total eclipse will be visible to people in parts of Africa, the Middle East and Asia, according to NASA.

Blood moons are not unusual occurrences. Still, these dramatic celestial events have inspired both awe and alarm throughout the centuries ― including among some fringe segments of American Christianity that take the appearance of blood moons to be a sign that the apocalypse is drawing nearer.