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Q & A: Stars in pictures of astronauts on the moon

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Most recent answer: 10/22/2007
Q:
Whenever I see clips of when the astronaunts or on the moon, there are never any stars in the back round, why is this?
- Anonymous
A:
Well, the sun is a star, and it should be plenty visible to the astronauts and their photographers on the moon. Maybe they were careful not to point their cameras directly at the sun for fear of damage.

As for all the other stars, they are much fainter than the sun. The lunar surface, when illuminated by sunlight, is very bright. The astronauts' helmet visors were metallized to reflect most of this (sunglasses built right in). The range of brightnesses which are recorded by a camera is limited -- brighter than some maximum is white, and dimmer is black. Set a camera so it records an astronaut and the surrounding lunar surface reasonably, and the sky will look black (except for the sun and the Earth). Set the camera so the stars are visible, and the astronaut and the lunar surface will look all white ("washed out"). Itís pretty hard to take pictures of stars with ordinary cameras even on a dark night. The shutter has to be left open a long time to collect enough light to see the stars. Stars should appear to be brighter when viewed on the moon because of the lack of air to dim their light, but with those sunglass-like visors on, Iíll be the astronauts themselves had a tough time seeing them, if at all.

Tom

(published on 10/22/2007)

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