On 8 Jun 2004 16:05:47 -0700, (LSL) wrote:

I've been watching the Cassini stuff, and something struck me that
I've never really thought too much about before, so I'm hoping this
isn't the proverbial stupid question!

When I see these images of planets within our solar system, why do I
never see stars in the backdrop (at least that I can remember?)

Not a stupid question at all. We are accustomed to seeing stars in the night
sky, so our intuition tells us that they should be visible in all those space
images. But in fact, most planets are so much brighter than the stars that when
exposed correctly, the stars just don't make it above the noise level. The Moon
is a good example. It is about the same brightness as a freshly surfaced parking
lot in full sunlight.That's why you set your camera to typical daytime exposure
levels when shooting it. Such an exposure won't show the stars. Figure that
planetary exposures are on the order of milliseconds, stellar exposures are on
the order of seconds. For an image of the Moon or planet to show stars, it would
need to be grossly overexposed.

_________________________________________________

Chris L Peterson
Cloudbait Observatory
http://www.cloudbait.com