A Blue Banded Blood Moon: Unraveling the Colors of a Lunar Eclipse
Lunar eclipses paint our night sky with spectacular colors, but a particularly intriguing sight is the appearance of a distinct blue band gracing the eclipsed Moon. While often subtle, this phenomenon was beautifully captured and digitally enhanced in a recent HDR image of the March 14, 2025 lunar eclipse, taken from Norman, Oklahoma.
The Natural Colors of the Moon
In the featured image, you'll notice the upper right portion of the top lunar disk exhibits a natural gray hue. This is the part of the Moon directly illuminated by sunlight, unaffected by the eclipse.
The Crimson Glow: The Blood Moon Effect
The lower sections of the Moon in all three images are not bathed in direct sunlight. Instead, they reside within Earth's shadow. This area appears faintly lit and takes on a red or 'blood moon' coloration. This occurs for the same reason Earth's sunsets appear red: as sunlight passes through Earth's atmosphere, the air molecules scatter away blue light more effectively, allowing the longer, red wavelengths to reach us.
The Enigmatic Blue Band
The truly fascinating element in this capture is the purple-blue band visible in the upper right of the top and middle images. This striking color is a result of sunlight that has journeyed through the uppermost layers of Earth's atmosphere. Here, ozone plays a key role. Unlike the lower atmosphere where red light is scattered more, ozone in the higher atmosphere absorbs red light more efficiently, allowing blue light to pass through and tint the eclipsed Moon. This is why the blue band, though real, is often challenging to observe without digital enhancement.
