LPOD Feb 11, 2008

SCOOTING ALONG

image by Paco Bellido

Yesterday I took some pictures of a 39 hours Moon and I noticed a star near the limb, some minutes after the star was a bit farther. We see the Moon rising on the East and setting on the West, most of the apparent motion of the Moon across the sky is the result of Earth rotation, but the Moon itself also moves, about 4% of the apparent motion of the Moon across the sky is due to the Moon's movement in its orbit. To an observer on Earth, the Moon takes about 2 minutes to move its own diameter to the west. From one night to the other the Moon travels about 13 degrees to the East. This motion is quite noticeable if you measure the apparent distance to a fixed star with a short time span.

Paco Bellido

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