What is a Supermoon?

Have you ever heard the term supermoon and wondered what makes this lunar event special? Simply put, a supermoon occurs when a full moon coincides with the Moon’s closest approach to Earth in its orbit. This alignment is what makes the Moon appear larger and brighter than usual.

Unlike the standard full moon that happens roughly once a month, a supermoon is linked to the Moon’s elliptical path around our planet. Because the orbit isn't a perfect circle, the Moon’s distance from Earth varies. When it reaches its closest point, called perigee, and is fully illuminated by the Sun, we see a supermoon.

What Does “Supermoon” Really Mean?

• Super: Refers to the Moon being at or near its closest orbital point to Earth.
• Moon: The familiar natural satellite we see in the night sky, shining by reflecting sunlight.
• Full Moon: The phase when the entire face of the Moon is illuminated.

This combination results in a moon that looks up to about 14% larger and 30% brighter than a typical full moon viewed when the Moon is farther away.

Keep in mind, the difference isn't usually dramatic to casual sky watchers, but for photographers and astronomy enthusiasts, it offers a fantastic opportunity to capture a strikingly detailed and luminous moon.

The Moon’s journey around Earth is far from a perfect circle. Instead, it follows an elliptical orbit, meaning its distance from Earth varies over time. This variation is key to understanding why sometimes the Moon looks bigger and brighter—setting the stage for the supermoon phenomenon.

Elliptical Orbit Explained

Unlike a circular path, an elliptical orbit means the Moon swings closer and then farther away from Earth during each cycle. Two important points on this orbit are:

• Perigee: The closest point to Earth, where the Moon can appear larger and more luminous.
• Apoapsis (often called apogee): The farthest point from Earth, where the Moon appears smaller.

How the Orbit Affects Moon’s Appearance

When the Moon is near perigee during a full moon, it appears noticeably larger to observers on Earth. This is because the apparent size of the Moon depends on the distance to Earth—closer means bigger. Conversely, a full moon near apogee looks smaller and less striking.

Orbital Timing and Cycle

The Moon completes one full orbit around Earth roughly every 27.3 days (sidereal month), but the timing of perigee shifts slightly with each orbit. This shifting means the exact distance of the full moon from Earth changes each month.

Understanding these orbital basics helps you grasp why supermoons are special—and why their timing can vary from month to month.

What exactly is a Supermoon? Simply put, it’s a full moon that appears larger and brighter than usual because it is closest to Earth in its orbit. This closest point is known as perigee.

Understanding Perigee

The Moon orbits Earth in an elliptical (oval-shaped) path, not a perfect circle. This means the distance between the Moon and Earth changes as it travels:

• Perigee: The Moon’s closest approach to Earth, typically around 225,000 miles (363,000 kilometers).
• Apogee: The farthest point in the orbit, roughly 252,000 miles (405,000 kilometers) away.

When a full moon coincides with perigee, the Moon appears up to about 14% larger and 30% brighter in the sky compared to a full moon at apogee. This visually striking event is what we call a Supermoon.

Why “Supermoon”?

The term “Supermoon” was popularized by astrologer Richard Nolle in the 1970s to describe a new or full moon that occurs within 90% of perigee. However, in common usage, it’s mostly tied to the full moon phase at or near perigee.

Visual Impact and Measurement

Though the size difference might seem subtle, many observers notice the Supermoon’s enhanced presence when it rises near the horizon. Photographers and astronomers track these moments to take advantage of the Moon’s enhanced brightness and size.

Why does a Supermoon look so striking? When the Moon is at its closest point to Earth in its elliptical orbit—called perigee—it appears noticeably larger and brighter than usual. This proximity can make the full Moon look up to 14% bigger and 30% brighter compared to when it is at its farthest point, or apogee.

Perceived Size: The Moon Illusion

Besides the actual size difference, a Supermoon can also seem larger due to a well-known optical effect called the Moon illusion. When the Moon is near the horizon, our brains compare it to familiar objects like trees or buildings, making it appear even more enormous than it physically is. So, a Supermoon rising or setting offers a truly spectacular sight!

Brightness and Color Variations

The extra brightness of a Supermoon is subtle but noticeable, especially in a dark sky. Atmospheric conditions at moonrise or moonset can add warm hues—soft oranges, reds, or yellows—enhancing the visual drama. This combination of size, brightness, and color often creates memorable viewing experiences.

• Size: Up to 14% larger diameter than a typical full Moon.
• Brightness: Can be about 30% brighter due to closer proximity.
• Color: Often richer near the horizon due to atmospheric scattering.

Understanding these factors helps you appreciate why Supermoons captivate observers and photographers alike, turning a familiar celestial face into an extraordinary spectacle.

Supermoons don’t light up the sky every month. They occur only when a full moon coincides closely with the Moon’s perigee—the point in its elliptical orbit where it’s closest to Earth. Because the Moon’s orbit is not a perfect circle, this distance varies from month to month.

How Often Do Supermoons Happen?

Typically, there are about 3 to 4 supermoons each year. However, the exact number can vary based on the year’s lunar cycle and the specific criteria used to define “supermoon.” Some years might see just two, others up to five.

Timing Within the Lunar Cycle

• Full moon timing is key: A supermoon must occur during the full moon phase to appear especially bright and large.
• Perigee alignment: The Moon needs to be within about 90% or less of its closest distance to Earth compared to its average orbit.
• Orbital variations: Because the Moon’s elliptical orbit slowly shifts over time, the timing of supermoons gradually changes from year to year.

This means some full moons may be near perigee but not close enough to qualify as a supermoon, while others may appear just a bit bigger and brighter without being at the exact closest point.

Tracking future supermoon dates is straightforward using astronomical calendars or apps, which can help you plan your best moon-watching or astrophotography sessions.

The moon offers a variety of captivating phenomena beyond just the supermoon. To fully appreciate a supermoon’s uniqueness, it helps to compare it with other well-known lunar events:

Blue Moon

A Blue Moon is a calendar-based event, defined as the second full moon in a single calendar month. Unlike the supermoon, it doesn’t depend on the moon’s distance from Earth but rather the timing of the lunar cycle. Blue moons occur roughly every 2.5 to 3 years and don’t typically look any different visually.

Blood Moon (Total Lunar Eclipse)

The Blood Moon happens during a total lunar eclipse, when Earth’s shadow falls on the moon, giving it a reddish or coppery glow. This event is caused by sunlight filtering through Earth’s atmosphere, not by the moon’s orbit. Blood moons are dramatic and rare, combining a full moon with an eclipse, but they are unrelated to the supermoon’s proximity.

Harvest Moon

The Harvest Moon is the full moon closest to the autumnal equinox. It earned its name because its bright light traditionally helped farmers harvest crops late into the evening. The Harvest Moon can sometimes be a supermoon, but its timing is seasonal rather than orbital.

Micromoon

In contrast to the supermoon, a Micromoon occurs when the full moon is at its farthest point from Earth (apogee). This makes the moon appear smaller and dimmer in the sky.

Understanding these distinctions can deepen your appreciation for each lunar event and help you anticipate what you’re actually seeing when you look up at the night sky.

Choose the right time: The best moments to observe or photograph a supermoon are during moonrise or moonset. At these times, the moon often appears larger and more colorful near the horizon due to atmospheric effects, creating striking images.

Scout your location: Find a site with a clear view of the horizon, away from city lights if possible. Light pollution can wash out the moon’s details and reduce contrast in your photos.

Observation Tips

• Give your eyes time to adjust: Moonlight can be surprisingly bright. After stepping outside, allow a few minutes for your eyes to acclimate to the darkness to better appreciate subtle lunar features.
• Use binoculars or a telescope: Even a modest telescope can reveal the moon’s craters, maria, and mountain ranges in stunning detail. Binoculars offer a portable alternative for quick lunar viewing.
• Stay patient: Atmospheric conditions like haze or clouds can affect visibility. Waiting for clearer skies can significantly improve your experience.

Photography Tips

• Use a telephoto lens: A focal length of 200mm or more helps capture the lunar disk with great detail. For smartphones, consider clip-on zoom lenses for better framing.
• Stabilize your camera: Use a tripod to avoid blur caused by hand shake, especially at longer exposures or higher zooms.
• Manual settings are key: Set your camera to manual mode. Start with a low ISO (100–400), a shutter speed around 1/125 to 1/250 seconds, and adjust aperture for sharpness (f/8–f/11 is ideal).
• Focus precisely: Use live view focusing or manual focus to lock in sharpness on the moon’s edge.
• Bracket your shots: Take multiple photos at different exposures to capture the moon’s bright surface as well as darker shadow details.

With a bit of preparation and patience, viewing and photographing a supermoon can be a rewarding experience that deepens your appreciation for our closest celestial neighbor.

Choosing the right optical gear can greatly enhance your experience when observing a supermoon. The Moon’s surface features—craters, maria, and mountains—reveal fascinating details at moderate magnification, making the right telescope or binoculars essential for both beginners and seasoned skywatchers.

Binoculars: Simple, Portable, and Effective

For those just starting out or wanting quick lunar views, binoculars provide a wide field of view and easy handling. Look for models with at least 7x magnification and objective lenses of 35mm or larger. This combination balances brightness and detail without excessive shakiness.

• Pros: Lightweight, affordable, and versatile for other astronomical targets.
• Cons: Limited magnification — lunar details won’t be as crisp as through a telescope.

Telescopes: Unlocking Lunar Detail

Telescope designs vary, but for moon viewing, common types include refractors, reflectors, and catadioptrics. Here’s what to keep in mind:

• Magnification: Aim for 50x to 100x for ideal lunar detail without dimness or blurring.
• Aperture: A 70mm to 130mm aperture gathers enough light for sharp, bright views.
• Portability: Consider size and weight if you plan to travel to darker skies.
• Mount: A sturdy tripod or mount reduces shake, critical at higher magnifications.

Additional Accessories

• Barlow Lenses: Double or triple your telescope’s magnification without changing eyepieces.
• Moon Filters: These reduce glare and eye strain, enhancing contrast on bright lunar phases like the supermoon.
• Smartphone Adapters: Attach your phone to capture impressive moon photos through your optics.

While binoculars offer ease and portability, a quality telescope opens a window to a lunar landscape rich with textures and shadows—perfect for appreciating the supermoon’s grandeur.

Myth 1: Supermoons are huge, dramatically larger than normal full moons. While a supermoon can appear noticeably bigger and brighter than a typical full moon, the size difference is subtle—around 7% larger and up to 15% brighter. This change is usually only obvious when the moon is near the horizon, thanks to an optical illusion known as the Moon Illusion.

Myth 2: Supermoons cause extreme natural disasters. It's a common misconception that supermoons trigger earthquakes, volcanic eruptions, or tsunamis. Although the moon’s gravitational pull affects ocean tides, the difference caused by a supermoon is minimal and not linked to significant geological events.

Myth 3: Supermoons are rare celestial events. Supermoons occur several times a year, depending on the lunar orbit and timing. The moon’s elliptical orbit brings it close (perigee) multiple times, so supermoons are more frequent than many assume.

Other Common Confusions

• Supermoon vs. Blue Moon: A blue moon refers to the second full moon in a calendar month, not a size change.
• Supermoon vs. Blood Moon: A blood moon is a total lunar eclipse where the moon appears reddish, unrelated to its distance.
• “Supermoon” is an official astronomical term: It was popularized in media but is not formally recognized by all astronomical organizations.