OPOD - Subtle Sky Colours

Last updated on September 16, 2023

OPOD - Subtle Sky Colours: Unveiling the Enigmatic Beauty of Atmospheric Optics

The mesmerizing world of atmospheric optics never ceases to amaze us with its ethereal displays. Among these captivating phenomena, the subtle colors of the sky hold a special place. While circumzenithal arcs and rainbows boast pure and vibrant hues, the colors of a moon corona are a complex blend, revealing an enigmatic beauty that leaves us in awe.

In a stunning composite image captured by P-M Hedén on December 22nd, 2010, in Sweden, we are granted a glimpse into the intricate nature of coronal colors. The photograph showcases the moon corona, a celestial phenomenon formed by the diffraction of light through cloud droplets suspended in the atmosphere. Unlike the vivid colors seen in circumzenithal arcs or rainbows, the hues within a corona are more subtle and nuanced, hinting at the intricate interplay of light and matter.

To comprehend the complexity of coronal colors, it is essential to understand their formation. The angular diameter of the rings depicted in the image provides valuable insights. Comparing this measurement with a Mie scattering calculation conducted by IRIS (Institute for Research in Schools) reveals that the cloud droplets responsible for diffracting light were approximately 20 microns (0.02mm) in size. This information unveils the delicate nature of these atmospheric particles, contributing to the captivating blend of colors observed within the corona.

Another intriguing aspect highlighted by P-M Hedén's composite image is the drastic difference in brightness between the corona and its light source, the moon. With an exposure ratio of 1000:1, capturing this stark contrast in a photograph is nearly impossible. However, our eyes effortlessly handle this remarkable range of luminosity, allowing us to appreciate the beauty of the corona without difficulty.

The ethereal colors within a moon corona serve as a testament to the intricate dance between light and matter in our atmosphere. As sunlight passes through the cloud droplets, it undergoes various interactions, including diffraction, scattering, and reflection. These interactions result in the dispersion of light into its constituent wavelengths, revealing a palette of subtle hues that adorn the sky.

It is worth noting that this article has been automatically converted from the old site and may not appear as originally intended. Nevertheless, it provides a captivating glimpse into the mysterious world of atmospheric optics. For those seeking to delve deeper into this subject, exploring the original article is highly recommended.

In conclusion, the enchanting colors of a moon corona unveil the hidden beauty and complexity of atmospheric optics. With their subtle blend of hues, these ethereal phenomena remind us of the intricate interplay between light and matter in our atmosphere. As we gaze at the sky, let us marvel at the enigmatic nature of these optical displays, and embrace the awe-inspiring wonders that surround us.

Moon Corona pictured in Sweden 22nd December 2010 by P-M Hed�n (Clear Skies - Astro & Sky Images, TWAN member). ©P-M Hed�n, shown with permission.

P-M's composite image - 0.8s for the corona and 1/1300s for the moon tells us much. It reveals the subtlety of coronal colours each hue a complex mixture rather than the purer colours of a circumzenithal arc or rainbow.

It gives the angular diameter of the rings. Comparison with a Mie scattering calculation by IRIS shows that the cloud droplets diffracting light were about 20 micron (0.02mm) across.

And the exposure ratio of 1000:1 speaks of the enormous brightness difference between a corona and its light source, almost impossible to span in a photograph but one that human eyes handle easily.

Note: this article has been automatically converted from the old site and may not appear as intended. You can find the original article here.

Reference Atmospheric Optics

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