Noctilucent Clouds and Crescent Moon
September 23, 2003
Astronaut Ed Lu, aboard the International Space Station (ISS), captured this beautiful photo showing a thin sliver of the crescent Moon and silvery noctilucent clouds. He used a Kodak DCS760 digital camera equipped with a 400mm lens to make this shot on July 27, 2003 -- the ISS was over central Asia at the time. Noctilucent clouds are most easily observed at high latitudes (generally above 50 degrees latitude) during the summer months, and they can be seen from the ground as well as from space. These shiny looking clouds appear somewhat similar to cirrus clouds and form in the polar mesosphere (between about 75-90 km or 39 and 56 miles or above the Earth’s surface). They're optically thin and can only be observed during twilight hours, when the Sun is below the horizon and illuminates the highest levels of our atmosphere.