When the moon passes into Earth’s shadow during a lunar eclipse, it often takes on a reddish hue. But sometimes a blood-red ring can be seen around the full moon when no eclipse is taking place. This strange halo has been observed and puzzled over for centuries.

If you’re short on time, here’s a quick answer: The red ring around the moon is caused by ice crystals and dust particles in the upper atmosphere refracting light at a specific angle.

In this comprehensive guide, we’ll explore the optical phenomena that create lunar halos. You’ll learn why rings can appear red, blue, or other colors. We’ll also look at the role of ice clouds, altitude, and weather conditions in producing these circles around the moon.

What Causes a Halo Around the Moon?

Many of us have marveled at the sight of a beautiful halo surrounding the moon on a clear night. But have you ever wondered what causes this mysterious phenomenon? Let’s delve into the science behind it.

Refraction of moonlight through ice crystals

One of the main causes of the halo around the moon is the refraction of moonlight through ice crystals in the Earth’s atmosphere. When the moonlight passes through these ice crystals, it gets bent or refracted, causing it to spread out and create a halo effect.

This phenomenon is similar to how light is refracted through a prism, resulting in the formation of a spectrum of colors.

Dispersion of light into spectrum of colors

As the moonlight passes through the ice crystals, it not only gets refracted but also dispersed into a spectrum of colors. This is why we often see a ring of colors around the moon, with red being the innermost ring and violet being the outermost. It’s truly a mesmerizing sight!

HIGH and LOW atmospheric cirrus clouds

Another factor that can contribute to the formation of a halo around the moon is the presence of high and low atmospheric cirrus clouds. These clouds, made up of tiny ice crystals or water droplets, can also refract and disperse moonlight, creating a halo effect.

The size and shape of the ice crystals or water droplets in these clouds play a role in determining the size and shape of the halo.

Dust and other particles in the air

Lastly, dust and other particles in the air can also play a role in the formation of a halo around the moon. These particles can scatter and reflect moonlight, contributing to the halo effect. The amount and composition of these particles can vary depending on factors such as weather conditions and human activities, which can result in different types of halos.

It’s important to note that the appearance of a halo around the moon is not a paranormal or supernatural event. It is simply a natural optical phenomenon that can be explained by science. So, the next time you spot a halo around the moon, take a moment to appreciate the beauty and wonder of nature’s spectacle!

When Halos Appear Red vs Other Colors

Have you ever looked up at the night sky and noticed a mysterious red ring around the moon? This phenomenon, known as a lunar halo, has fascinated people for centuries. But what causes this red color, and how does it differ from halos of other colors?

Red – due to long wavelengths refracting

The red color of a lunar halo is due to the refraction of light by ice crystals in the Earth’s atmosphere. When light passes through these ice crystals, it is bent or refracted. The longer wavelengths of red light are bent more than the shorter wavelengths of blue and green light.

As a result, we see a ring of red light surrounding the moon.

This phenomenon is similar to what happens when sunlight passes through the Earth’s atmosphere during sunrise or sunset. The longer wavelengths of red and orange light are scattered less by the atmosphere, giving the sky its vibrant colors.

Blue and green – shorter wavelengths

While red is the most common color seen in lunar halos, it is not the only color that can appear. Halos of blue and green hues can also be observed under certain atmospheric conditions. These colors are created when the ice crystals in the atmosphere refract shorter wavelengths of light.

Interestingly, the presence of other atmospheric particles, such as dust or pollution, can also affect the color of a lunar halo. These particles can scatter and absorb certain wavelengths of light, leading to variations in color.

Size of ice crystals affects color

The size of the ice crystals in the atmosphere can also influence the color of a lunar halo. Larger ice crystals tend to produce a more intense red color, while smaller crystals may result in a paler or even white halo.

Additionally, the shape of the ice crystals can play a role in the appearance of the halo. Hexagonal crystals, for example, are responsible for creating the distinct circular shape of a lunar halo.

Color fringing explained

One interesting aspect of lunar halos is the phenomenon of color fringing. This occurs when different colors appear to separate and form a ring around the moon. The explanation lies in the way light is dispersed by the ice crystals.

As light passes through the crystals, it is not only refracted but also scattered in different directions. This scattering causes the different colors to spread out, creating the distinct rings of color seen in a lunar halo.

Role of Altitude and Weather Conditions

The mysterious red ring around the moon is a fascinating phenomenon that has captured the curiosity of sky gazers for centuries. While its appearance may seem otherworldly, there are scientific explanations behind this intriguing optical phenomenon.

One of the key factors that contribute to the formation of the red ring is the altitude at which the moon is positioned and the prevailing weather conditions.

HIGH altitude cirrus clouds

One of the main culprits behind the red ring around the moon is the presence of high altitude cirrus clouds. These wispy, icy clouds form at altitudes of approximately 20,000 feet or higher and are composed of tiny ice crystals.

When the moonlight passes through these ice crystals, it gets refracted, causing the light to scatter and create a ring-like appearance around the moon. The unique properties of these high altitude cirrus clouds make them an ideal medium for this optical phenomenon to occur.

Temperature, humidity, pressure

The temperature, humidity, and pressure conditions in the atmosphere also play a crucial role in the formation of the red ring around the moon. In colder months, when the air is colder and drier, the likelihood of the formation of high altitude cirrus clouds increases.

These conditions create the perfect environment for the ice crystals to form, leading to the scattering of moonlight and the subsequent appearance of the red ring.

Before/after frontal system passes

Another factor that can contribute to the presence of the red ring around the moon is the movement of a frontal system. Before a frontal system passes, there is often a change in the atmospheric conditions, including an increase in moisture and the formation of high altitude cirrus clouds.

As the frontal system passes, it can bring with it the necessary conditions for the red ring to form, heightening the chances of witnessing this intriguing phenomenon.

More common in colder months

While the red ring around the moon can occur throughout the year, it is more commonly observed during the colder months. This is due to the combination of lower temperatures, drier air, and an increased likelihood of the presence of high altitude cirrus clouds during this time.

So, if you ever find yourself gazing at the moon on a cold winter night, keep an eye out for the mesmerizing red ring that might appear around it.

Documenting and Appreciating Lunar Halos

When it comes to celestial phenomena, one of the most captivating sights is the mysterious red ring around the moon, also known as a lunar halo. This awe-inspiring spectacle often leaves people in awe and wondering about its origins and significance.

In this article, we will delve into the world of lunar halos, exploring how they are documented, their historical accounts, the art of photographing them, and upcoming opportunities to witness these mesmerizing events.

Citizen Science – Recording Sightings

Thanks to the power of citizen science, individuals from all walks of life can actively contribute to the documentation of lunar halos. Amateur astronomers, nature enthusiasts, and even casual sky gazers can report their sightings of lunar halos to various platforms and organizations dedicated to monitoring celestial events.

By submitting their observations, these citizen scientists help create a comprehensive database that aids in further understanding the occurrence and frequency of lunar halos. One such platform is the Citizen Science website, which encourages people to share their experiences and contribute to scientific research.

Historic Accounts and Symbolism

Lunar halos have fascinated humanity for centuries, with numerous historical accounts and cultural symbolism associated with them. In ancient times, these halos were often seen as omens or signs of impending change.

For example, in certain cultures, a red ring around the moon was believed to herald the arrival of storms or the coming of a significant event. Today, while we understand the scientific explanation behind lunar halos, it is still fascinating to explore the cultural heritage and the stories that have been passed down through generations.

Photographing these Transient Events

Photographing lunar halos requires a combination of patience, skill, and the right equipment. Capturing the ethereal beauty of these transient events can be a rewarding experience for both amateur and professional photographers alike.

With the advancements in camera technology and the availability of online resources, it has become easier than ever to learn the techniques and settings required to capture stunning images of lunar halos.

Websites like Photography Talk offer tips and tutorials to help photographers make the most of these rare opportunities.

Upcoming Moon Halo Viewing Opportunities

If you’re eager to witness a lunar halo yourself, it’s essential to stay informed about upcoming opportunities. While lunar halos can occur throughout the year, certain periods, such as during the winter months or in regions with high humidity, are more favorable for their formation.

Weather websites, such as the Weather Channel, provide forecasts and moon phase calendars, enabling sky gazers to plan their stargazing outings in advance. Additionally, local astronomy clubs and observatories often organize special events centered around lunar halos, offering the chance to observe these captivating phenomena under expert guidance.


While they appear mystical, lunar halos have a scientific basis in the refraction of moonlight. These temporary rings around the moon are created by precisely aligned ice crystals high in our atmosphere.

Observing and documenting halo moons allows us to appreciate the intersection of atmospheric optics, weather, and our solar system alignments.

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