From: henry@spsystems.net   
      
   In article , User  wrote:   
   >Are there standard (optical) cameras on space probes...   
      
   Well, "standard" is pushing it -- they tend to be custom designs -- but   
   yes, many of the images you see published are taken in ordinary visible   
   light.  The colors are sometimes exaggerated or otherwise off, because the   
   image has been computer-enhanced or the spectral bands of the camera don't   
   match those of the human eye, but otherwise the image is roughly what you   
   could see from the same vantage point.  Typically you would have to use a   
   small telescope, mind you, because the cameras have those built in.   
      
   >...But some of the still photos I've seen appear to   
   >be plain old regular photos.  What I want to know is, if this is the case,   
   >where does the light come from?  I mean, when taking pictures of Uranus, for   
   >example, is there really enough light from the sun to fully illuminate the   
   >surface?  Or does the aperature on the camera stay open for long periods of   
   >time to collect a lot of light?   
      
   Yes, the light is sunlight.  It's a lot dimmer than it is here, but it   
   still illuminates things well enough.  They *do* often use relatively long   
   exposures, and the cameras for outer-planet spacecraft often have fairly   
   large apertures to gather more light (in the same way that large   
   binoculars give you a brighter view at night here).   
      
   >Or do the atmospheres of the planets   
   >themselves give off some sort of illumination?   
      
   No, apart from occasional lightning and auroras (which have sometimes   
   been photographed).   
   --   
   "Think outside the box -- the box isn't our friend."    |   Henry Spencer   
                                   -- George Herbert       | henry@spsystems.net   
      
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