: While I'm sure Sagan considers it sacrilegious, that wouldn't be
: because of his doubtfull credibility as an astronomer. Modern, 
: ground-based, visible light astronomy (what these proposed
: orbiting billboards would upset) is already a dying field: The
: opacity and distortions caused by the atmosphere itself have
: driven most of the field to use radio, far infrared or space-based
: telescopes.

Hardly.  The Keck telescope in Hawaii has taken its first pictures; they're
nearly as good as Hubble for a tiny fraction of the cost.

: In any case, a bright point of light passing through
: the field doesn't ruin observations. If that were the case, the
: thousands of existing satellites would have already done so (satelliets
: might not seem so bright to the eyes, but as far as astronomy is concerned,
: they are extremely bright.)

I believe that this orbiting space junk will be FAR brighter still;
more like the full moon.  The moon upsets deep-sky observation all
over the sky (and not just looking at it) because of scattered light.

This is a known problem, but of course two weeks out of every four are
OK.  What happens when this billboard circles every 90 minutes?  What
would be a good time then?

:                                              Frank Crary
:                                              CU Boulder
