Lunar eclipse colors, signatures of ozone

The red/green/blue lines denote the relative intensity (normalized to the sum r+g+b) from left to right along the center line (averaged vertically across 50 pixels). While red is the prevailing color in the central umbra (left), near the border with the penumbra a blue color component shows up.

The lunar eclipse yesterday (July 27, 2018) provided an excellent opportunity to take pictures and to study the color of Earth’s shadow. I snapped some images with my smartphone (Huwai Mate 10 Pro, Leica camera) through a 130mm Newton telescope. The moon was pretty low and within the city barely visible. Just after leaving the central shadow cone, the bluish color of the umbra/penumbra region became very noticeable. Today, I analyzed the picture a bit and drew the relative red/green/blue components along the shadow. Indeed blue wins within a narrow stripe bordering the penumbra. According to the literature, this is a signature of the ozone layer (which absorbs orange and red light, while blue passes and arrives at the moon).

More images:


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