What a blue super moon actually is
A blue super moon combines two separate astronomical circumstances: a supermoon and a blue moon. A supermoon occurs when a full moon or new moon coincides with perigee, the Moon’s closest approach to Earth in its elliptical orbit, making the Moon appear larger and slightly brighter than average. A blue moon is the modern popular definition of the second full moon in a single calendar month. When these two conditions align, the result is a full moon that is both visually larger and, under certain atmospheric conditions, potentially bluer in appearance.
The name can be misleading, as the Moon does not turn a vivid blue on most occasions. Instead, under particular circumstances such as volcanic eruptions or large dust storms, particles in the upper atmosphere can filter out red light and scatter blue light, giving the Moon a bluish tint. The term has evolved from historical uses to today’s widely accepted calendar meaning, making it useful for planning, observation, and photography.
How blue super moons form: astronomy and atmospheric science
Blue super moons are defined by two intersecting cycles: the lunar orbital period and the synodic month, the interval between full moons. Because the Moon’s orbit is elliptical rather than circular, its distance from Earth varies. At perigee, the Moon can appear up to about 14 percent larger and shine roughly 30 percent brighter than at apogee. Meanwhile, the modern definition of a blue moon as the second full moon in a calendar month occurs about once every two to three years. When a perigee full moon coincides with this calendrical blue moon, the stage is set for a blue super moon.
Atmospheric conditions determine whether the moon actually looks blue. Particles sized around 0.5 to 1 micrometer—such as those from volcanic eruptions, wildfire smoke, or dust storms—scatter red light and allow blue light to reach an observer’s eyes. Historic events like the 1883 eruption of Krakatoa produced widespread blue moons for years afterward. Clean, stable air typically gives full moons a warm, yellow or orange hue near the horizon, so a genuinely blue moon is relatively rare even when the geometry aligns.
Observing a blue super moon: practical tips
Observing a blue super moon requires little more than clear skies and a view of the Moon, but a few practical steps improve the experience. Choose a location with an unobstructed view toward the horizon or your preferred framing element. Arrive early to scout your composition if you plan to photograph the Moon with landmarks or trees. For visual observation, no special equipment is required, but binoculars or a small telescope can reveal surface features such as craters and lunar maria.
Timing matters: the full Moon appears largest near moonrise due to a common optical illusion, though it is actually the same size at zenith. Check local moonrise and moonset times, and aim to be set up before the Moon emerges if you want to capture it through trees or cityscape. If you’re using a camera, start with a longer focal length—such as a 200 mm lens or telephoto setting—and use a sturdy mount or stable support to minimize blur. Manual focus on the lunar limb for the sharpest results.
Simple checklist for a safe and successful viewing session
- Check the forecast for clear skies and low humidity.
- Pick a spot with an open view toward the Moon’s path.
- Arrive early to set up and compose your shot or sightline.
- Use a red-light torch if you need illumination without ruining night vision.
- For photography, use a tripod, shutter release or timer, and a moderate ISO.
Blue super moon photography: settings and safety
Photographing a blue super moon is accessible with modern cameras and smartphones, yet it benefits from planning and technique. Start with a stable platform: a tripod is ideal, but a table, wall, or car hood can work in a pinch. Use a remote release, self-timer, or shutter release app to avoid camera shake. If your camera has a mirror lock-up or electronic front curtain, enable it to reduce vibration. Focus carefully on the lunar limb or use live view and digital zoom to confirm sharpness. Bracketing exposure can help you capture both the Moon’s surface detail and any atmospheric effects.
Smartphone photographers can achieve strong results using the digital zoom or an added telephoto lens, and by tapping to set focus and exposure. Avoid handling the phone during long exposures; consider using a small tripod or steady rest. Eye safety is straightforward: observing the Moon with the naked eye or through standard optics is entirely safe. Do not look directly at the Sun, and avoid using unapproved solar filters on cameras or telescopes unless they are specifically designed for solar observation.
Notable blue super moons and how to compare them
The timing and characteristics of blue super moons vary by decade due to the interplay of orbital mechanics and calendar structure. Below is a factual summary of recent and upcoming examples, based on published astronomical data. Note that visibility of a blue color depends on local atmospheric conditions rather than the Moon’s distance alone.
| Date | Moon phase | Approx. distance at perigee (km) | Apparent diameter comparison to average | Notes |
|---|---|---|---|---|
| 31 August 2023 | Full | 357,362 | ~7–8% larger than average | Coincided with a seasonal blue moon; no notable blue tint observed globally |
| 31 January 2018 | Full | 356,852 | ~7–9% larger than average | Followed by a total lunar eclipse; atmospheric effects produced blue hues in some regions |
| 31 March 2018 | Full | 362,428 | ~4–5% larger than average | Second full moon of the month; clearer definition of a calendar blue super moon |
| 30–31 October 2020 | Full | 360,067 | ~5% larger than average | Northern Hemisphere visibility; weather-dependent color effects |
| 31 July 2025 | Full | 357,283 | ~7% larger than average | Projected blue super moon for some regions depending on atmospheric conditions |
Quick comparison: supermoon vs blue moon vs blue super moon
- Supermoon: Full or new moon occurring near perigee, appearing larger and brighter.
- Blue moon: The second full moon in a calendar month (or, less commonly, a third full moon in a season with four full moons).
- Blue super moon: A full moon that is both a supermoon and a blue moon; visually larger, and potentially bluer under specific atmospheric conditions.
Common myths and realities
Several misconceptions surround blue super moons, often amplified by sensational headlines. Claims that a blue super moon can trigger extreme tides, natural disasters, or visible color changes in most events are not supported by evidence. While the Moon does influence tides, a supermoon’s additional effect is modest—on the order of a few centimeters in tidal range—and well within normal variability. The Moon’s apparent color can shift due to atmospheric particles, but this is uncommon and highly dependent on local conditions, not on the mere fact of a supermoon.
Another myth is that blue super moons are exceedingly rare. They occur on a predictable, if infrequent, schedule when calendar and orbital cycles align. Understanding the underlying mechanics helps separate fact from exaggeration and supports better planning for observation and photography.
Planning ahead: seasonal and regional considerations
Because blue super moons depend on both orbital mechanics and the Gregorian calendar, their frequency is irregular. They can occur two or three times in a decade or cluster several years apart, depending on how perigee intervals align with monthly cycles. Visibility is influenced by local weather, light pollution, and viewing geometry. In the Southern Hemisphere, seasonal differences and lunar declination can affect the Moon’s path across the sky and the clarity of atmospheric viewing conditions.
For reliable planning, consult almanacs or astronomical services that provide perigee times, full moon moments, and atmospheric forecasts. Pairing this information with local horizon profiles helps you anticipate how the Moon will appear in your area and at your chosen time. Tracking past events and future projections improves your ability to recognize conditions favorable for a distinctly bluish appearance.
Closing: how to use this information today
To make the most of a blue super moon, focus on clear-sky planning, safe viewing practices, and realistic expectations. The Moon will appear larger and brighter during a supermoon, and under the right atmospheric conditions it may take on a subtle blue tone. Use a tripod, practice framing, and check timing details to enhance observation or photography. Remember that color shifts are driven by particle scattering in the atmosphere, not by the Moon itself, and that no verified method can guarantee a blue hue. With these facts and practical steps, you can approach each blue super moon with confidence and clarity.