The moon phases of May 2018 moved through a complete lunar cycle in just over 29 days, beginning with a waning gibbous moon and ending with a fully illuminated face in the constellation Scorpius. For skywatchers, the month offered a clean, predictable rhythm: a quiet last quarter, a dark new moon, a brightening first quarter, and a Full Flower Moon on May 29. Because the phases fell roughly a week apart, anyone with a modest telescope, a pair of binoculars, or simply a clear view of the western horizon had multiple chances to follow the terminator line as it swept across craters, maria, and mountain ranges.
What made May 2018 particularly rewarding was how the lunar cycle lined up with the rest of the night sky. A brilliant Venus dominated the evening twilight, Jupiter had just reached opposition in early May, and the Eta Aquarid meteor shower peaked while the moon was still fairly bright. The dates below use Coordinated Universal Time, so observers in the Americas, Europe, Asia, and Australia may find that the local calendar date shifts by a day depending on their time zone. That single detail explains why two people on opposite sides of the planet can disagree about which night the moon looked "full."
The May 2018 Lunar Calendar: Key Dates and Phase Times
May 2018 contained four principal phases, evenly spaced across the month. The last quarter arrived on May 8 at 02:09 UTC, the new moon on May 15 at 11:48 UTC, the first quarter on May 22 at 03:49 UTC, and the full moon on May 29 at 14:19 UTC. That spacing is the natural consequence of the moon's 29.53-day synodic period, the interval between two identical phases as measured from Earth. Each phase is technically an instant, not a night, even though the moon looks close to that phase for roughly a day on either side.
For practical observing, the moments just before and after each listed time are usually the most useful. A quarter moon at exactly first or last quarter shows a perfectly straight terminator, which is excellent for judging crater relief along the day-night boundary. A new moon is invisible, but the days surrounding it offer the darkest skies of the month for deep-sky viewing. The full moon, by contrast, washes out faint objects but turns the lunar surface into a bright, flat-looking disk that is better suited to casual viewing than to detailed study.
| Phase | Date (2018) | Time (UTC) |
|---|---|---|
| Last Quarter | May 8 | 02:09 |
| New Moon | May 15 | 11:48 |
| First Quarter | May 22 | 03:49 |
| Full Moon | May 29 | 14:19 |
Last Quarter on May 8 and the Eta Aquarid Meteor Shower
The month opened with the moon in a waning gibbous phase, shrinking toward last quarter on May 8. During this stretch, the moon rose late in the evening and climbed higher toward dawn, which meant early risers got the best views. The illuminated portion shrank from roughly two-thirds down to exactly half by the morning of the 8th. In the days that followed, the moon became a thinning crescent visible only in the pre-dawn sky, gradually losing its grip on the darkness.
The Eta Aquarid meteor shower peaked on the nights of May 5 and 6, right in the middle of this waning phase. The shower, produced by debris from Halley's Comet, favors the Southern Hemisphere but still delivers a respectable number of swift meteors to northern observers before dawn. With the moon more than half illuminated and rising after midnight, the faintest meteors were lost to its glare. Even so, patient observers who looked away from the moon's direction still caught a handful of bright, fast trails radiating from the constellation Aquarius.
New Moon on May 15 and the Return of the Evening Crescent
May 15 brought the new moon, the point at which the lunar disk sits between Earth and the Sun and disappears entirely from view. This is the darkest window of the month, and around the 13th through the 17th, observers could hunt for faint galaxies, globular clusters, and nebulae without the moon intruding on their dark-adapted vision. It is also the phase when the moon's gravitational pull combines with the Sun's to produce the largest spring tides, a useful detail for anyone who walks tidal flats or photographs coastal scenery.
Within a couple of days, the young crescent returned to the western twilight. By May 17, the waxing crescent hung low in the sky near brilliant Venus, a pairing that made for one of the most photogenic scenes of the month. Because the crescent was only a few degrees wide, the faintly lit portion of the disk became visible through earthshine, the sunlight reflected off Earth that softly illuminates the moon's night side. It is an effect best seen in the first few evenings after a new moon, and May 2018 provided a textbook example.
The Full Flower Moon of May 29, 2018
The full moon on May 29 closed out the month at 14:19 UTC, meaning that observers in Europe, Africa, and Asia saw it at its roundest that evening, while much of North America caught a nearly indistinguishable version of the same event on the night before or the night after. The May full moon carries the traditional name Flower Moon, a reference to the blooming season across much of North America. Other folk names include the Corn Planting Moon, the Milk Moon, and the Hare Moon, each tied to agricultural or seasonal markers.
Naming conventions aside, this full moon had a genuine astronomical distinction. Because the Sun sits in Taurus and Gemini during late May, the anti-solar point falls in the constellation Scorpius and Ophiuchus, placing the full moon remarkably close to Antares, the red supergiant that anchors the scorpion's heart. The moon passed within a few degrees of that star, producing a striking contrast between cold white moonlight and Antares' ruddy glow. A bright moon also tends to wash out nearby stars, so the pairing was more about proximity than visual drama through the eyepiece.
The Flower Moon's Close Approach to Antares
Antares is roughly 550 light-years away and is one of the largest stars visible to the naked eye, with a diameter that would swallow the orbit of Mars if it replaced the Sun. Seeing the moon drift past it is a reminder of scale: the moon is about 1.3 light-seconds from Earth, while Antares is hundreds of thousands of times farther away. Their apparent closeness in the sky is pure line-of-sight coincidence, the same trick that makes the moon appear to pass in front of planets during an occultation.
On the night of May 28 into May 29, the moon tracked across the sky roughly alongside Antares, rising in the east and setting in the west. Observers who watched over several hours could see the moon's position relative to the star change noticeably, a direct demonstration of the moon's eastward orbital motion of about 13 degrees per day. That slow drift is why the moon rises roughly 50 minutes later each night, and why the phase you see tonight will look noticeably different a week from now.
Photographing and Tracking the May 2018 Lunar Cycle
Capturing the phases of May 2018 required very little specialized equipment, but a few choices made a large difference in results. For close-ups of craters along the terminator, a telephoto lens of at least 200mm or a small telescope with a camera adapter produced the sharpest detail during the quarter phases. For wide twilight shots of the crescent with Venus or the full moon with Antares, a tripod and a short exposure of a few seconds were usually enough, provided the camera was set to manual focus and the ISO kept low to control noise.
Tracking the cycle day by day is arguably more valuable than any single photograph. Observers who sketched or imaged the moon on May 15, 18, 22, 25, and 29 built a clear record of how the illuminated fraction grew from 0 to 100 percent, and how the terminator moved from west to east. Repeating that exercise in any month reveals the same underlying geometry, which is why the lunar calendar remains one of the most accessible entry points into observational astronomy for beginners and experienced amateurs alike.
May 2018 is long behind us now, but its pattern is not. The same sequence of last quarter, new moon, first quarter, and full moon plays out every 29.5 days, so anyone who missed the Flower Moon near Antares can simply wait for the next cycle and start watching a few days after the new moon. Grab a pair of binoculars on the next clear evening, look west just after sunset, and the crescent will do the rest of the work for you.