Sunday, 22 March 2009

Why can't you see stars or galaxies in the photographs that show the curvature of the Earth and part of the black background of space?

From Frequently Asked Questions About Astronaut-Acquired Photographs

The reason you can't see stars in high oblique photos is that the film speed is too slow and the shutter speed is too fast. Most of the films used are 100 ASA color positive. Fast shutter speeds are used to eliminate blur from the motion of the spacecraft. These films and shutter speeds would not be suitable for photographing stars from the Earth either. One exception to this rule is when astronauts use films and camera settings specifically to photograph features such as the Aurora Borealis and Aurora Australis. In these cases stars also show up in the photograph. The photos are also slightly blurry because very long exposures are needed to capture these dim nighttime features.

Example photograph of the Aurora Australis that includes stars

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