Re: [ATM] HRI nasa telescope mirror -

["Ben McIlwain" <cydeweys@gmail.com>]

On 10/16/07, David Adams <elrey314159265359@yahoo.com> wrote:
>Ben wrote:
>> I'm guessing whoever bought that wants it more for the historical
>> value, because a 12" f/30 just isn't that practical for land-based
>> use.
>
> It seems like it would be even less practical in space!?

Not when you consider the point of Deep Impact's mission.  It didn't
need a lot of light-gathering ability, because it was only, what, a
few hundred kilometers away from the comet it was observing during the
impact?  It's not like looking at distant stars, or even trying to
look at other planets from Earth.  Light-gathering wasn't really a
problem for them: they just needed good angular resolution.  And the
best way to get good angular resolution in a light-weight system (for
launching into space) when light-gathering ability doesn't matter so
much is to use a small-diameter, lightweight primary mirror with a
really long focal length.  Note that it's a Cassegrain design, so some
of that long focal length is folded inside the tube.
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