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Old 08-12-2008, 09:10 AM
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[1ponders] (Paul)
Retired, damn no pension

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Join Date: Nov 2004
Location: Obi Obi, Qld
Posts: 18,778
The other thing you need to remeber too Kirk is that if you double your f/ratio (f/5 > f/10) Then you increase the time required to achieve the same level of brightness by a factor of 4. Now this may not be a problem with widefield, but for narrow field work increasing an exposure from 5 min to 20 min puts a lot more demand on your mount's quality and autoguiding abilities.
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