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Re: Why Longer Focal Length for Planetary?

Subject: Re: Why Longer Focal Length for Planetary?
From: Stuart Levy
Date: 15 Jul 2005 10:34:24 -0500
Newsgroups: sci.astro.amateur
In article <42D76280.9DDC5608@xxxxxxxxx>, Marry wrote:
> Here's an answer Professor Morrison gave in 1953:
> 
> "Longer focal length optics produce more stable higher resolution images,
> because the longer focal length optics give light a long tube to stabilise
> in. It can be shown that in the shorter tube telescopes light does not have
> the time or distance to settle down from its journey through space and
> the turbulent atmosphere. Light which can be stretched out in a long tube
> vs a short tube, has both the time and the distance to settle down and rid
> itself of turbulences, which affords a much better image at the receiving 
> end."
> 
> You cant beat them apples (explained by a professor of physics)!
> 
> Mary

Wow.  A physicist said *that*?  Sounds like an answer worthy
of Ask Dr. Science! 

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