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   Moonset from Earth Orbit 












 
Moonset from the ISS. On 16th April '03 Don Pettit, the ISS science officer, imaged the full moon as it set behind the Earth's limb. In this montage the relative positions of the moon are computed from the image times and the ISS orbital period.
As the ISS spun, the moon's light dipped ever deeper into the earth's atmosphere before leaving again. The path length is double that the setting moon seen from earth's surface and the distortion by differential atmospheric refraction is correspondingly greater.

At first the lower limb is distorted most as the atmospheric lens pushes the lower limb upwards to create an egg shape (close-up). Finally the whole moon becomes an impossibly flattened oval. In the final frame the moon's lower edge is slightly clipped by the earth's surface.

The lower part of the disk and then the entire moon is appreciably reddened by preferential atmospheric scattering of blue light out of the ray path.

Individual images NASA/JPL: composite ©Les Cowley