Spectacular Moon Photo Caught Over Chile

This story was updated at 3:36 p.m. EDT.

The huge full moon setting in the high Chilean desert dominates a spectacular new photo caught in Chile just as astronomers closed up their observatory after a long, busy night.

The photo, released Monday, shows a dazzling full moon as it sets behind the Very Large Telescope (VLT) in Chile's Atacama Desert while dawn approaches, coloring the sky with deep hues of blue and purple. The moon was last full on May 27 and appears larger than normal in the photograph, but it is actually an optical illusion.

"Contrary to what one may think, this picture is no montage," wrote officials with the European Southern Observatory (ESO), which operates the VLT, in a statement.?"The moon appears large because it is seen close to the horizon and our perception is deceived by the proximity of references on the ground." [More full moon photos.]

The large size of the full moon is known as "the moon illusion." It is caused by our mind's attempt to make sense of the moon in relation to earthly objects on the horizon.

In the photo, the moon appears to sit on a plateau just behind the VLT observatory. In reality, it is about 30,000 times farther away, ESO officials said.

ESO staff member Gordon Gillet caught this view of the moon illusion from a distance of about 8.6 miles (14 km) from the VLT observatory using a 500-mm telephoto lens. He snapped the photo from the nearby peak of Cerro Amazones, the future home of the enormous 137-foot (42-meter) European Extremely Large Telescope (E-ELT), which would be the world's largest telescope when complete in 2018.

Amateur skywathers can see the moon illusion too without a camera to prove that the full moon on the horizon ? either during moonrise or moonset ? is no larger than the moon at any other time or location. To try it, hold a small object, such as a pencil eraser, at arm's length and compare its size to that of the rising moon. Then go back out a couple hours later, when the moon is higher and seems smaller, and make the same comparison.

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