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Re: [ATM] F/10 or F/8?

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Subject: Re: [ATM] F/10 or F/8?
From: "Bob May" <bobmay@nethere.com>
Date: Tue, 14 Jun 2005 10:46:32 -0700
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The difference between 8 and 10 is really minimal.  Better to go towards
something longer for planetary viewing.  For a 6" mirror, you'll be using
something like 300x and you want to be able to do that without getting too
small of a EP.  This tends to make a really long scope (150" would be how
long for a 12mm EP - put a 2x barlow in front of that and your focal length
drops to 75") of at least F12 (note the 12mm barlowed uses a F12 focal
length for the 300x) and longer than that would be nice.
I'll note that the commercial scopes are built to one focal length as they
are all made on the same tooling and as a result, the tube just gets fatter
as you go up on the diameter of the primary.
Bob May
bobmay@nethere.com
http://nav.to/bobmay
http://bobmay.astronomy.net

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References:
- [ATM] F/10 or F/8?
  - From: Curtis Spivey <curtis.spivey@gmail.com>

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