On Sat, 8 Feb 2003, Randall Clague wrote:
> >There are things Hubble has been doing for a
> >decade that those ground-based telescopes will *never* do.
>
> I was trying to imagine what some of those things might be... Hubble
> Deep Field. No ground based telescope - correction, no Earth based
> telescope - can look at the same patch of sky for hours and hours and
> hours and hours without blinking.
Yep.
And Hubble works farther into the infrared, and much farther into the
ultraviolet, than any ground-based scope can.
And it has a much darker sky background, which matters when working on
very faint objects.
And it can point closer to the Sun, although its cautious operating
policies limit that.
And it can observe rapid time variations without a lot of superimposed
atmospheric noise.
And -- minor but not entirely insignificant -- it has a clear view of the
entire sky, something that is quite difficult to achieve from any single
point on Earth.
And, finally, although its high resolution has been exceeded by adaptive
optics and interferometry on the ground, its high resolution comes with
many fewer ifs, ands, and buts. Adaptive optics requires either nearby
bright guide stars, or still-experimental laser guide stars. Imaging
interferometry can observe only bright sources, because you need a fair
number of photons per millisecond to detect interference fringes.
Henry Spencer
[EMAIL PROTECTED]
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