A micromoon is a full moon that occurs when the Moon is relatively far from Earth, near the most distant part of its orbit. The Moon itself does not shrink. Its disk simply takes up a little less space in the sky, much as a distant ball looks smaller than an identical ball nearby.
That makes a micromoon the counterpart of a supermoon: one emphasizes the far end of the Moon’s distance range, the other the near end. Neither is a separate lunar phase, and neither changes the familiar pattern of bright highlands and dark plains on the Moon’s face.
The interesting question is not whether the size difference exists—it does—but how large it is and whether you can notice it. A consistent photograph can reveal a change that is surprisingly difficult to judge by looking at a full moon alone.
What qualifies as a micromoon?
There is no universally adopted astronomical cutoff for the word micromoon. It is a popular descriptive label, rather than a formally defined class of celestial object. You may therefore find different distance thresholds or timing rules in different publications. Some also apply the term to a distant new moon, although an ordinary new moon is not visible as a bright disk.
On this site, a micromoon is a full moon farther than 405,000 km from Earth’s center. That center-to-center measurement is called geocentric distance. It gives one consistent reference, rather than a distance that changes with an observer’s location on Earth’s surface.
As a dated example, the full moon of 18 July 2027 has a geocentric distance of 406,220 km and meets that definition. For current phase dates and exact full-moon times, use the moon phase calendar.
The phrase apogee full moon describes the underlying situation: a full moon near the farthest point of the lunar orbit. It does not necessarily mean the instant of full moon and the instant of apogee are identical. A micromoon label can cover a full moon close enough to apogee to fall beyond the chosen distance threshold.
Why apogee and full moon do not always coincide
The Moon follows an elliptical orbit, not a perfect circle. The closest point to Earth is perigee; the farthest point is apogee. Its mean distance is 384,400 km, while typical perigee and apogee distances are 363,300 km and 405,500 km respectively. Those typical values are not fixed limits: the Sun’s gravitational influence helps make the actual distances vary from orbit to orbit.
Distance and phase describe different things. Distance tells you where the Moon is along its stretched orbit. Phase tells you how much of its sunlit hemisphere faces us. Full moon occurs when the Moon lies approximately opposite the Sun in Earth’s sky, whether the Moon happens to be near perigee, apogee, or somewhere between them.
The mean cycle from one new moon to the next, the synodic month, lasts 29.53059 days. The cycle from one apogee to the next is a different orbital rhythm. Because those rhythms do not match, the Moon does not return to the same distance at every full moon.
This is why a run of full moons can gradually shift from relatively close to relatively distant. A micromoon is the meeting of two conditions—full phase and large distance—not an extra stage inserted into the phase cycle.
How much smaller does it look?
For an object as distant as the Moon, apparent diameter is approximately inversely proportional to distance. Double the distance and the disk would look about half as wide. The lunar distance range is much narrower than that, so the real change is modest.
Using the typical distances above, divide 363,300 by 405,500. The result is about 0.896. That means the Moon at typical apogee looks about 10.4 percent smaller in diameter than it does at typical perigee. This comparison isolates distance; it does not require both positions to occur at full moon.
A comparison between two dated full moons gives a slightly different result. The supermoon of 24 December 2026 is 356,927 km away, while the micromoon of 18 July 2027 is 406,220 km away. Dividing 356,927 by 406,220 gives about 0.879: the micromoon’s disk is approximately 12.1 percent narrower than that supermoon’s disk.
The wording matters. Reverse the comparison and the supermoon is about 13.8 percent wider than the micromoon, because the smaller disk is now the baseline. Both statements describe the same pair of moons.
For a broader explanation of close full moons, see what a supermoon is. The site classifies those as full moons closer than 360,000 km, using the same geocentric reference as its micromoon threshold.
Make a fair visual or photographic comparison
A micromoon still looks like a normal full moon. Most people do not have a precise visual memory of the Moon’s diameter from weeks or months earlier, so looking up and deciding that it seems small is not a reliable test. The Moon illusion complicates matters further: a Moon near the horizon can appear unusually large even though that impression is not caused by it moving closer to Earth.
Photography offers a cleaner comparison. Use the same camera, lens, focal length, and image dimensions for both full moons. Avoid resizing one image separately, and compare original files rather than screenshots that may have been scaled differently. Photograph the Moon well above the horizon when possible, where atmospheric distortion is less troublesome.
Suppose the closer full moon spans 1,000 pixels in your image. For the dated pair above, the farther full moon should span about 879 pixels under otherwise comparable conditions. That is a measurable difference, even if it was not obvious through the viewfinder. The prediction is approximate because the observer-to-Moon distance is not exactly the geocentric distance, and observing geometry can differ between sessions.
Use the city moon dashboard search to find local moonrise and moonset, altitude, azimuth, distance, and a sky view with local weather. Those details help you choose sessions with similar lunar altitude rather than comparing one Moon low on the horizon with another high overhead.
If including a building or tree, keep the camera position fixed too. Moving farther from the foreground and using a longer lens can make the Moon appear much larger relative to that object. That photographic effect can easily overwhelm the genuine size difference between a micromoon and a supermoon.
A smaller disk is not a dimmed lunar eclipse
Distance affects more than diameter. The apparent area of a circular disk changes with the square of its diameter. For the dated comparison above, 0.879 squared is about 0.772, so the micromoon occupies roughly 23 percent less apparent area than the supermoon.
Under otherwise equal illumination and viewing conditions, a smaller full-moon disk also delivers less total light to the observer. That does not mean every patch of lunar terrain looks proportionally darker. The same landscape is compressed into a smaller angular area; total received light and surface brightness are different quantities. Haze, clouds, altitude, and camera exposure can make casual brightness comparisons misleading.
A lunar eclipse is a separate effect. It happens when the Moon passes through Earth’s shadow, not when the Moon reaches apogee. A micromoon does not automatically turn red, acquire a dark bite, or lose its full phase. To check actual shadow events, the lunar eclipse catalog provides eclipse types, contact times, durations, and visibility from your location.
The distinction is useful when interpreting photographs: a uniformly smaller full disk points to distance or image scale, while a moving shadow across the disk points to an eclipse. Micromoon describes where the Moon is in its orbit; eclipse describes what is happening to the sunlight reaching it.