Section 1.1: The Enigmatic Gloria

The optical phenomenon known as gloria has been documented since as early as 63 AD, when it was spotted from Mount Emei in China. During that period, it was referred to as the "light of Buddha," since the halo consistently surrounded the observer's shadow, often seen as a symbol of enlightenment or a connection to Buddha.

Gloria manifests as vibrant rings encircling the observer's shadow projected onto a cloud. While the exact mechanism behind gloria's formation remains elusive, it is thought to result from the diffraction of light reflected by water droplets within the cloud, similar to the way a rainbow forms.

The shadow itself is linked to a widely recognized optical occurrence known as the Brocken spectre, which is frequently seen in conjunction with gloria. The unique characteristic of the Brocken spectre is that it casts a shadow onto a cloud or fog, creating the illusion that the shadow is floating in the air and moving independently, a result of the shifting clouds or fog. To experience gloria, one must ascend high into the mountains on a cloudy day and align their shadow with the fog or cloud below. Notably, gloria can also be witnessed around the shadow of an airplane, although capturing this phenomenon while flying is considerably more challenging than in mountainous regions.

Section 1.2: Parhelion (Sun Dog)

An ancient Ukrainian literary work, "The Tale of Igor’s Campaign," recounts an event where "four suns shone over the Russian land" prior to the invasion of the Polovtsians. The warriors interpreted this as an omen of impending disaster, likely witnessing a phenomenon known as parhelion.

Parhelion is a solar halo that occurs when light refracts through tiny ice crystals suspended in the Earth’s atmosphere, predominantly found in cirrus clouds. During a parhelion event, multiple "false suns" may appear on either side of the actual Sun at the same elevation.

This phenomenon is often observed alongside another optical marvel — the solar halo. Parhelion, similar to halos, occurs when the sky is filled with cirrus clouds. Each ice crystal in the cloud acts as a miniature prism, allowing light to enter through one face, refract at 22 degrees, and exit through another, thus creating a beautiful halo around the Sun or Moon. A 22-degree halo forms when the ice crystals are randomly oriented, while vertically aligned crystals can produce the "false suns" characteristic of parhelion.

Section 1.3: Moonbow

The moonbow has captured the fascination of many throughout history. Aristotle, the ancient Greek philosopher, was among the first to mention it in his work "Meteorology."

Similar to a standard rainbow, which is produced by sunlight, a moonbow arises from the light of the Moon. Unlike solar rainbows, moonbows lack the vivid brightness and often appear light gray to the naked eye, though they are actually composed of multiple colors. This muted appearance is due to the relatively weak intensity of moonlight, making it challenging for humans to detect the full range of colors. However, when captured in long-exposure photographs, the moonbow reveals its stunning colors.

To observe a moonbow, several conditions must align: the Moon should be at or near the full phase, positioned low in the sky, and viewed against a dark background. Additionally, moonlight must reflect off water droplets, which typically occurs during or shortly after rain, especially near waterfalls. Consequently, moonbows are predominantly photographed over waterfalls, as illustrated above.

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