If you’ve ever pointed a telescope at the Moon around the first quarter, your eye has almost certainly been drawn to a monumental trio on the northern edge of Mare Nectaris (the Sea of Nectar). The youngest and sharpest member of this “trio” is Theophilus, which has earned the admiration of astronomers not only for its size but also for its dramatic structure.

The “Lunar Triumvirate”

Theophilus is not a lone wolf. Together with two other craters, Cyrillus and Catharina, it forms a spectacular chain that perfectly illustrates the passage of time on the Moon:

Theophilus (The youngest): Sharp edges, clean shapes. It has clearly settled on top of its neighbor.

Cyrillus (The middle one): The impact of Theophilus partially crushed its northeastern wall. Its shapes are already more worn.

Catharina (The Old One): This is the southernmost member. Its edges are blurred, and its interior is pockmarked by smaller impacts—a true veteran.

It offers the most beautiful view when the terminator (the boundary between light and shadow) is passing right by it. At that moment, the grazing light highlights the shadows of the central peaks, which stretch across the crater’s flat floor. I captured exactly that moment in this photo.