Lunar Observing Guide: Craters, Seas, and the Best Moon Phases

You step outside on a clear evening and there it is — the Moon, impossibly bright and detailed, hanging right above you. It's the first thing most of us ever looked at through a telescope, and yet it remains one of the most rewarding objects you can observe. The trick is knowing when to look and where to point your eyepiece.

In this guide, you'll learn how the Moon's phases change what you can see, which features to look for first, and how to turn casual glances into meaningful observing sessions that deepen your appreciation of our nearest neighbor.

Why the Full Moon Is Actually the Worst Time to Observe

This surprises almost every beginner: the full Moon is beautiful to look at with the naked eye, but through a telescope it's flat, washed-out, and almost featureless. Why? Because when the Sun illuminates the Moon head-on, there are no shadows. And shadows are what make craters, mountains, and valleys pop into three-dimensional relief.

The ideal times to observe the Moon are during the crescent and quarter phases — roughly 3 to 10 days after new Moon (waxing) or 3 to 10 days after full Moon (waning). During these phases, the terminator sweeps across different parts of the surface each night, giving you a changing landscape to explore.

Your First Lunar Tour: The Must-See Features

The Great Craters

The Moon's surface is covered in impact craters, from tiny pits to massive basins hundreds of kilometers across. Here are the showpieces you should seek out first:

• Tycho — A relatively young crater near the Moon's south pole, surrounded by a spectacular ray system that stretches across much of the lunar surface. Best seen near full Moon when the rays are brightest.
• Copernicus — A textbook complex crater with terraced walls, central peaks, and its own ray system. Stunning when the terminator passes through it around day 9.
• Clavius — One of the largest craters visible, with a chain of progressively smaller craters along its floor. A wonderful sight in any telescope.
• Plato — A flat-floored, dark crater on the northern shore of Mare Imbrium. Its smooth floor contrasts dramatically with the rugged terrain around it.
• Aristarchus — The brightest crater on the Moon, so reflective it can sometimes be glimpsed with the naked eye during earthshine.

The Lunar Seas (Maria)

The dark, smooth areas on the Moon's surface are called maria (singular: mare), Latin for "seas." Early observers thought they might be oceans, but they're actually vast plains of solidified basaltic lava that flooded ancient impact basins billions of years ago.

The major maria you can identify include:

• Mare Tranquillitatis (Sea of Tranquility) — Where Apollo 11 landed in 1969
• Mare Serenitatis (Sea of Serenity) — A beautifully circular basin northeast of center
• Mare Imbrium (Sea of Rains) — The largest and most prominent mare, bordered by mountain ranges
• Oceanus Procellarum (Ocean of Storms) — The largest dark area, spanning the western face

Mountain Ranges and Valleys

Along the borders of the maria, you'll find impressive mountain ranges. The Lunar Apennines, bordering Mare Imbrium, rise to peaks over 5,000 meters — comparable to the terrestrial Alps. When the terminator crosses these mountains, their peaks catch the sunlight while the valleys below remain in darkness, creating a breathtaking play of light and shadow.

Equipment for Lunar Observing

The good news is that the Moon is bright and detailed enough to reward any optical instrument:

• Binoculars — Even a basic pair reveals the major maria, the brightest craters, and the terminator's shadow play. A great starting point.
• Small telescope (60-90mm) — Hundreds of craters become visible, along with mountain ranges and rilles. This is where lunar observing truly comes alive.
• Medium telescope (4-8 inches) — Fine detail emerges: crater chains, collapsed lava tubes, tiny craterlets on the floors of larger craters, and subtle color differences in the maria.

If you don't yet own a telescope, our guide on choosing your first telescope will help you find the right instrument. And if you already own binoculars, check out our binoculars for astronomy guide to get the most from them.

A Phase-by-Phase Observing Calendar

Each night the terminator moves, revealing new terrain. If you observe the Moon on consecutive nights around first quarter, you'll watch an entirely new landscape emerge from the shadows — it's like exploring a new continent each evening.