The Moon, photographed from Space Shuttle Columbia on STS-107

The photo above shows a sight that can only be seen from space: The Moon against a black sky, with the Earth in daylight. Fewer than .00001% of the world’s population have had the opportunity to see this sight. That number will increase dramatically in the next few years, when suborbital spaceflight becomes commercially available.

At first glance, the Moon appears oddly dark. We think of the Moon as being quite bright, almost pure white. That’s because we’re used to viewing the Moon at night when our eyes are dark adapted. Of course, the Moon isn’t really white, or light in color, at all. The observations and photos taken by the Apollo astronauts, the samples they brought back, all prove that. Viewed alongside the oceans and clouds of Earth, the Moon shows its true color in this photograph.

The Moon also appears unusually small in this photo. That is due to the well-known Moon illusion, or rather the lack of a Moon illusion. When we observe the Moon in the night sky, our brains trick us into seeing the Moon as larger than it really is. That doesn’t happen when you look at a photograph of the Moon. The photo above is optically accurate, but the photo below has been altered to show the scene as you might actually perceive it from space, due to the Moon illusion:

Simulated Moon illusion

The following photograph also shows the Moon from space. In this photo, the Moon appears oddly distorted. This time, the effect you’re seeing is not the result of an illusion. This photograph was taken when the Moon was almost on the horizon. The Moon’s light crosses the boundary between the vacuum of space and the Earth’s atmosphere twice, first entering the atmosphere then leaving again. This causes a phenomenon known as atmospheric refraction, resulting in the optical distortion we see here.

You will also notice that the Moon appears lighter in this photo, closer to the way we are used to seeing it. That’s because the the photo was taken with a greater exposure. You can also see a few stars in this photograph. Stars are not visible in the photo above, which is exposed for the brightness of the Earth. As a result, the stars, which are much dimmer, cannot be recorded by the camera’s sensor. The limitation on a camera’s ability to simultaneously record very bright and very dim objects simultaneously is known as dynamic range, and it’s why you rarely see stars in photos taken from space. (A new technology, called High Dynamic Range photography, can overcome this limitation.)

Moon, photographed from International Space Station, flattened by atmospheric refraction

The following picture shows the Moon’s shadow on the Earth. Viewed from the surface of the Earth, this event would be seen as an annular solar eclipse. Because solar eclipses are rare, only a few astronauts have viewed such an event from space, mostly from Mir and the International Space Station. If a suborbital spaceflight occurred within the path of a solar eclipse, it would be possible to simultaneously view the eclipse from space and look back to see the Moon’s shadow on the Earth. Such a flight would no doubt be popular with both professional and amateur astronomers and photographers.

Moon's shadow on the Earth, as seen from space during an annular solar eclipse

Written by Astro1 on February 2nd, 2013 , Astronomy, Citizen Exploration

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COMMENTS
    Alexandre commented

    Thank you for the beautiful images and this insightful article.I was intrigued to know if the moon illusion worked in low earth orbit.

    Reply
    April 3, 2013 at 8:54 am
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