On Tue, 08 Jun 2004 23:25:34 GMT, "David Nakamoto" wrote:

You don't see the stars because even now CCD cameras don't have the dynamic
range of the eye. Being an avid imager of planets for almost the past year,
I can tell you that recording stars and planets clearly in the same image is
nearly impossible unless the star is of the nearly the same brightness as
the planet.

I don't entirely agree. Good CCD cameras have a dynamic range of 1:5000 to
1:10000, which is certainly enough to get a good planetary image showing stars.
For instance, if you expose Jupiter with such a camera, just filling the wells
with the brightest features, you will record stars to magnitude 10. With Saturn,
which isn't as bright, you can go even deeper.

What the many people, including the original poster, might fail to realize is
just how small a field a planet sits in when imaged from Earth, and how few
stars brighter then mag 10 are even in it (typically, none). This is pretty
apparent when you view Jupiter at high magnification with a small scope- there
may be no stars visible to the eye, or at least, very few.



The only advantage CCDs have over the eye is to save light over longer
periods of time, minutes instead of seconds, but this is not necessary for
the planets due to their high brightness.

I'd add the advantage of collecting data which can be manipulated. Thus,
structures with contrast differences too small to be discerned by the eye are
readily stretched into visibility in the digital realm. That's why CCD images of
even bright planets show so much more detail than ever shows up visually.

_________________________________________________

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